Darth Vader (I'm sure everyone knows what he's from)
Mega Houndoom - sig (Most evil looking Dark type I can think of) Aegislash (cause Lightsabers are essentially swords made of energy) Magnezone (Cause Magnemite bears a -slight- resemblence to a TIE fighter) Sharpedo (Dark type with extra coverage) Krookodile (same as Sharpedo) Lucario (represents the good left within him)
Could use a psychic to represent his signature force ability, Force Choke, but can't think of any that are particularly evil.
Since I don't know crap about posting spoiler tags, major Metal Gear Rising spoilers are heading this way. You've been warned.
Senator Armstrong. The fact that I was listening to this when I was looking at this thread may or may not have influenced my choice. http://www.youtube.com/watch?v=9bUMCPSlDn0
Signature Mon: Machamp, as it shares his buff physique and gets the "Man of action, not words" thing down perfectly.
Zoroark, because like how Zoroark is good at concealing it's identity until pushed, he's good at being able to keep his true goals hidden until pushed.
Braviary: It's a goddamn American eagle, and while he's fed up with how politicians are now, Armstrong strives to make America great again in his own way.
Metagross: Best way I can think of to represent Metal Gear Excelsus.
Electrivire: Both are powered up when hit by electricity.
Mega Gyarados: Given Gyarados' destructive nature and how it won't stomp rampaging until everything around it is a barren wasteland, it fits Armstrong's ultimate goal: to turn America into an anarchic wasteland itself. The Mega is just for extra oomph, as normal Gyarados could also work perfectly well for him.