I don't know about you guys, but I personally like to brainstorm new ideas for units, especially more unorthodox ideas that could stretch the definition of what kinds of unit concepts could fit various roles (such as raiders, riots, skirmishers, and assaults to name a few). Here are a few ideas that I have for some more unorthodox, possibly lethal joke, unit designs:
Serf (cheap construction unit): [Spoiler]
What if there were construction units that were so cheap, that they could be built en-masse, yet be balanced out by having far less buildpower and health (but especially buildpower) than other construction units? Perhaps, like Zerg Drones, they could sacrifice themselves in an attempt to build structures at an accelerated rate?
Legionnaire (cheap riot unit): [Spoiler]
So named because they may be as slow as your typical riot unit, but they're cheaper than even the cheapest raider unit, with their weapon of choice likely being a gauss gun that instantly hits, has a modestly-high rate-of-fire, has a range of about 350 (on par with a Mace), and is able to 1-shot Fleas. Not only could masses of them easily defeat most raiders of the same cost, but they could possibly defeat dps-based riot units of equal cost like the Reaper, Mace, and Redback (which could probably defeat lone Legionnaires in turn), along with most assault units that lack aoe. However, aside from possessing a riot unit's usual weakness to skirmishers, they would likely get demolished by aoe-based riot units like the Ripper, Outlaw, Venom, and Ogre to name a few.
Dervish (blink-teleporting melee unit): [Spoiler]
An alternative approach to using raiders to counter skirmishers, this unit may be slower than any other raider unit, and may be armed with nothing but melee weapons, but like a Protoss Zealot, it makes up for it with its ability to teleport a limited distance to quickly close the gap against enemy skirmishers. Although its stats and abilities would make it more troublesome for riot units to deal with (though its blink ability would have a cooldown period), ironically enough, units with superior range and speed (such as most scouts and raiders) could effectively counter them through kiting.
Fisher (ranged grappling unit): [Spoiler]
An alternative to using fast raiders to close the distance against skirmishers, this unit uses a grapple gun to pull skirmishers towards itself, allowing nearby friendly units (especially riots) to pick them off without the risk of moving too close to enemy lines. Unfortunately, it might be a bad idea pulling enemy riot units close to it.
Harvester (sweeping melee unit): [Spoiler]
Like an Ultralisk from StarCraft, this unit would use its faster-than-average speed and heavy armor to quickly close the distance against anything slower than a raider (which can counter it through kiting), and shred groups of enemies around it with its sweeping scythe-like blades. Especially dangerous against groups of skirmishers or aoe-based riots.
Leapfrog (walking anti-air missile): [Spoiler]
This suicidal unit is designed to be a cheap and effective way to counter bomber rushes. Although its range is too low to be of any use against long-ranged air units like the Nimbus, it will launch itself and explode into any air unit that dares to come too close.
Behemoth (slow-moving mobile fortress): [Spoiler]
Inspired by the Harkonnen Devastators from Emperor: Battle for Dune, this fairly pricey unit was designed to be a cheaper, more affordable answer to the Dante, in that, although they would lack the Dante's aoe capabilities, not only could a couple of them match one in combat with their rapid-firing 150mm autocannons, but they could do so at less than 2/3rds the price of one, and with a range of 600, allowing them to take on any kind of skirmisher unit, or even other non-strider heavy units like the Grizzly or Crab. Unfortunately, in order to make these units so powerful, yet so cheap and affordable, they could only afford a movement speed of less than 15 elmo/s, making them barely more mobile than a Desolator defense turret, which makes them especially vulnerable to precision artillery units like the Impaler, Lance, or Emissary, and bombers like the Raven or Likho, and makes them require support from transports or Djinns to allow them to get around the battlefoeld in a reasonable amount of time. Moreover, while their autocannons are powerful, they lack the rate-of-fire or splash damage needed to effectively deal with masses of cheap scouts or raiders, which the autocannons overkill, thus support from riot units is recommended.
Scourge (anti-heavy rover): [Spoiler]
The large missiles that the Scourge carries are designed for use against striders. Thus, like other anti-heavy units like Lances and Phantoms, while the Scourge's missiles deal massive damage, they lack in aoe, and have a long reload time. While possessing less range than the Lance, and while being unable to cloak like the Phantom, the Scourge is comparatively cheaper and faster than either unit.
Bulldozer (heavy blockade-running rover): [Spoiler]
Designed to break through heavy fortifications, this vehicle, despite its large size, is not only as durable as the likes of other front-line heavy units (including the Cyclops and Grizzly, and even some weaker striders like Dante or Scorpion), but despite its large size, it can move at speeds of over 90 elmo/s. Although the heat rays poking out from each of its four corners are suitable for quickly decimating enemy bases, along with whatever light units it gets close to (including anti-heavy sniper units like Lances or Phantoms), unfortunately, due to their low dps, lack of aoe, and limited firing arcs, they're inadequate against equal costs of assault units, other heavy units (including the aforementioned Cyclops, Grizzly, Dante, and Scorpion), or even the heavy base defenses that it's designed to go through, not necessarily overpower.
Troll (saturation skirmisher tank): [Spoiler]
Unusually for a skirmisher, the mortars fired by this unit have a modest blast radius, making it adept at not only kiting riot and assault units, but also killing scores of lesser skirmishers as well, though they're ineffective against more sturdier heavy units like Grizzlies. Moreover, due to the high trajectories that the shots travel at, they're not very effective against raiders, including groups of smaller ones.
Blackhawk (cruise missile bomber): [Spoiler]
Although an expensive and lightly-armored aircraft, the homing-capable cruise missiles fired by this long-range bomber allow it to safely attack targets from beyond the range of basic anti-air units or structures (including Razors or Threshers). Unfortunately, not only do the Chainsaw and Artemis still outrange it, but it's so slow that enemy Swifts and Raptors can easily catch up to it and shoot it down. (Note: I'd recommend adding long-range anti-air units for each factory to counter this unit, and making said long-range anti-air units both more expensive than, and not as deadly as, the shorter-ranged anti-air units in order to keep these long-range anti-air units from overshadowing the latter.)
Stirge (point defense aircraft): [Spoiler]
In order to give the air player more of a fighting chance at penetrating through enemy long-range air defenses such as Artemis or Chainsaw, sometimes all that's needed is a more expendable aircraft that can intercept enemy long-range SAMs, even if it means sacrificing its own life in the process. In the Stirge's case, it projects a wide bubble shield around it that serves to protect other aircraft from powerful projectiles, though when the shield goes down, then the shield generator overloads, causing the Stirge to explode. Unfortunately, the Stirge's shield is so weak, a single Razor, Thresher, Swift, or Raptor is enough to shoot down dozens of them at a time, in which case, it's usually more cost-effective to send the bombers alone anyways.
Zeppelin (slow-moving fortified airship): [Spoiler]
Inspired by the Kirov airships from Command & Conquer, Red Alert 2 & 3, these slow, ponderous airships make a Detriment seem fast by comparison. Although they are armed with short-ranged autocannons to support ground units within a modest range, anti-air units and structures easily outrange it, as do many skirmishers. So why would you want to build such a unit? Well, their biggest strength would be their absurdly high health pool for their cost, possibly supported by a potent shield to protect allied aircraft with. Not only would they be far cheaper to build than a Krow, they would have much higher health than one, possibly even as high as a Paladin, if not higher. With health that high, numerous Zeppelins could withstand enough hits from an Artemis to give accompanying bombers or gunships an opportunity to strike when the Artemis runs out of shots. Also, in the event that the Zeppelin finds itself above an enemy, it can use its D-gun ability to drop a devastating amount of bombs onto the enemy, similar to the Krow. Against a Chainsaw, a handful of Zeppelins could survive the onslaught just long enough for one of the Zeppelins to get within range of the Chainsaw, or at least survive long enough to distract the Chainsaw away from allied aircraft attempting to airdrop artillery support (or set themselves up in the case of artillery gunships like the Abaddon and Bombardier below) to destroy the Chainsaw. Finally, in the event that one is shot down, or set to self-destruct with Ctrl+D, it continues to move forward as it slowly falls into the ground, and upon contact with the ground, it explodes with the force of an exploding Singularity Reactor.
Roswell (gravity gunship): [Spoiler]
The saucer-like Roswell is equipped with the same graviton projectors that the Newton and Jugglenaut use, which allows it to either pull units towards itself, including lifting ground units into the air (which gives anti-air units a target to shoot at), and keeping enemy planes from retreating from it, but also repelling enemy units away from it, such as slowing down the advance of enemy bombers. Inspired by the Phoenix's secondary ability from StarCraft 2.
Abaddon (airborne wave motion artillery platform): [Spoiler]
The Abaddon is essentially a flying wave-motion particle beam cannon that is capable of laying waste to whatever's within its line of fire. When not shooting at targets, the Abaddon uses its wave-motion cannon to provide itself with extra thrust. However, when given a target in range (it can outrange any anti-air unit or structure in the game, save for the Chainsaw and Artemis), it needs to charge up its wave-motion cannon for a few seconds before it can fire a devastating beam of energy at its target for several more seconds, heavily damaging it, anything close around it, anything behind it, and anything directly between it and the cannon. Because of this, the Abaddon is useful not only for decimating striders, but also for bombarding a modest area (much like a saturation artillery unit like the Firewalker). Unfortunately, due to the impulse the wave-motion cannon provides to the user, it is too powerful to be usable by any ground unit (without causing the user to be thrown in the opposite direction), and even in the Abaddon's case, it needs to fire a particle beam behind it in order to keep itself stable, so care must be taken to ensure that friendly aircraft aren't caught in the crossfire. (The closest ground-based counterpart to this weapon is the immobile Starlight superweapon.) Moreover, during the weapon's cooldown time, the Abaddon can't rely upon the wave-motion cannon for thrust, causing it to move at reduced speed. Also, due to the cannon's design, the Abaddon cannot easily reposition or change targeting direction, making it ineffective against fast-moving raiders and interceptors.
Bombardier (deployable artillery gunship): [Spoiler]
Inspired by the Siege Chopper from Command & Conquer, Red Alert 2: Yuri's Revenge, the Bombardier is armed with a retractable howitzer which it can only deploy when it lands. Like the Impaler and Emissary, the shells that it fires are lacking in aoe, and are best used against individual targets. Moreover, the weapon's range is greater than that of any air defenses that aren't either an Artemis or a Chainsaw, and while landed, the gunship cannot be targeted by anti-air.
Prometheus (construction strider): [Spoiler]
At 1st glance, this unit might seem pointless, until you realize that this strider is, like the commander, not only tough, but capable of defending itself reasonably well, and between its strong shielding and high buildpower, unless it's met with a strong force, it could not only reclaim or terraform while under fire, but it could protect whatever it builds from enemies long enough to finish building them before they're destroyed.
Skyfeller (anti-air strider): [Spoiler]
Like the Airnomo from Supreme Commander 2, the vast array of long-range and short-range anti-air weapons that this strider provides should allow it to safely protect its fellow units from all but the most determined of airborne attacks. Unfortunately, aside from its high health pool, it lacks in any defensive capabilities against ground units.
Spirit (ultra-heavy saturation bomber): [Spoiler]
Built from a strider hub, this unit draws its inspiration from the Ahwassa from Supreme Commander: Forged Alliance (and is named after the real-life B-2 Spirit stealth bomber), in that not only is it very expensive (no less than a Paladin), and not only is it durable enough to fly over all but the most durable of anti-air defenses, and dump copious amounts of singularity bombs across an enemy base, but it would fly slowly, take forever to rearm, and have a really tough time making sharp turns, making it easily exposed to enemy aa fire from well past the target area. Alternatively, to keep it from being OP as soon as it starts flying, it could require that it stockpile bombs before it flies over its targets.
Ballista (precision artillery emplacement): [Spoiler]
A more modest alternative to the Cerberus and Big Bertha artillery emplacements, the Lucifer tachyon projector, and even the Tactical Missile Silo, the Ballista launches highly-precise ballistic missiles (similar to the ones that the Impaler launches) to attack most enemy base defenses from outside their range, even if the targets are unidentified. Unfortunately, the missiles don't track, lack in aoe, and have a high trajectory, making them ineffective against anything smaller and slower than a Detriment. Because of this, even if outranged by the Ballista, mobile artillery can serve as effective counter-artillery units against this structure. Moreover, while the Ballista can outrange the Lucifer, it cannot outrange the Cerberus.