Stormtroopers: Unflinchingly loyal and bring a wide variety of skills, including knowledge of logistics and advanced tech. Cons are that they can't hit shit. EDIT: Bear in mind, this is the supposedly feared fighting force that got curb-stomped by Ewoks.
- correction: they got curb-stomped because Vader was willing to let a bunch of clones get their butts handed to them by teddy bears while he and the Emperor played "We be Baaaaad Gloaty Jedi" with his son on a half-built space station. Blame the commanders. Not the troops. Yeah, they can't shoot for crap, but let's pay for some eyesight upgrades and more carrots in the canteen. Care and feeding? Easy. Communication? Built-in. They may suck as marksmen, but...well, more dakka. (This got my vote)
The Koopa Troop: Well, they're probably pretty chill guys... Just don't expect any actual conquest.
And they breathe fire. And they get routinely stomped because they can't figure out how to go in reverse. Denied.
Orcs: They get the job done, albeit sloppily. Having nigh-infinite hordes of them always helps, though they are prone to fighting among themselves when they don't have a common enemy. They are also very hard workers.
They also tend to want to eat captives, each other, bark off trees, and anything that looks like it wouldn't actually kill them outright. Pass.
Zombies: Why conquer the world when you can just slaughter the inhabitants? Having a blank slate to build your evil empire from is a lot easier than trying to subjugate the entire planet!
Except they have one thing they can do: eat. That's it. One trick. Eat. I could go be OverLord of Planet Nothing's The Hell HERE, is that what you're telling me? Oh, except zombies. Gee, let me think. PASS.
Cybermen: Resistant to conventional weapons, ruthlessly efficient, and deadly in combat, Cybermen are a force to be reckoned with. Their conversion tech can allow you to squelch rebellion after you've taken over. The only problem is that they don't take kindly to human authority figures.
Do I even need to say it?
The Roman Army: Loyal, efficient, and legendary, the Romans are an unstoppable force. At least, they were thousands of years ago. Now their archaic training means that they will take a while to adjust to modern combat, assuming they survive that long.
I'm sure they'd be fine with modern training and weapons. It's the whole "get ahead by screwing pretty much anyone you can in the back with a long sharp knife and getting your entertainment by throwing people into a pit and watching them hack or screw each other to death" that I have an issue with. I'm an overlord. OVERLORD. No usurpers. No quote of "Et Tu, Brute?" Shall. Pass.
Skynet: Arguably the most powerful force on this list, Skynet gives your army access to Terminators and time travel. The only problem is that you are more or less assured to be usurped and killed at some point.
Zombies, Cybermen, The Roman Army, and now a bunch of machines intent on destroying all mankind? This is less like a poll and more like a Stormtrooper love fest up in here.
The Martians: Death rays and aliens, what could possibly go wrong? Aside from the common cold?
For one, this cold I've been having a hell of a time shaking. *achoo* NPasth.
The truth, though, is that I'd simply prefer an army of Jem'Hadar. Assuming I'm a shifter, or at the very least considered one. That said, Stormtroopers are much closer.
