I normally do not put stickers on my car, I don't care what other people think and I can't see them myself anyway.
I have made exceptions: Led Zeppelin sticker on my mom's '84 Buick Regal that I drove; Yes, Grateful Dead, and Texas diver stickers on the Bronco I drove in college, that's about it.
Recently though I considered a Ron Paul sticker for his constitutionalism and 'end the Fed' agenda; my buddy also has a very cool-looking Springfield Armory sticker with the crossed cannons (which is also a patriotic thing to me).
I think I may go with a "Sic Semper Tyrannis (Thus Ever to Tyrants)" with Lady Liberty standing over a slain king, or a rattlesnake "Don't Tread on Me" sticker, or the same artwork with "Don't Taze Me, Bro" considering the current climate of our police, er, nanny state. Then again, why taunt the reactionaries?
Maybe I'll just go back to Led Zeppelin...