In films, I quess I'd have to put Chuck Norris on #1. There's a fucking internet meme about his bad-assness.
On #2, I have Leonidas (300). As someone said before, it takes balls to fight thousands of Persians with only 300 soldiers and almost win.
On #3 I put Zaraki Kenpachi from the anime Bleach. This guy's so badass, that he intentionally blocks out most of his power to make sure he doesn't kill his opponents too easily, because that wouldn't be any fun. Also, Kenpachi's fearlessness edges insanity. If he would actually master Bankai he'd be #1. No, pull that, he'd be #-1.
For games, there's really only Duke Nukem. Don't get me wrong, there's plenty of other badass characters, but they're ALL based on the proto-badassness of Duke Nukem. Just look at him:
Everything about him is badass. The picture is perfect. There's NOTHING to improve about his badassness. The army-haircut, the sunglasses, the big sigar, the bare, muscled arms, even the clothes he's wearing: everything is what you'd think of when you think badass.
But that's not even his coup de grace. That's his god damned one-liners. FUCK. There's just too many of them. When this guy opens his mouth, something awesome comes out. Always. If you'd take him imprisoned(hypothetically, because that's obviously impossible), take away his guns and tie him down on a chair, he'd just start talking about his balls of steel and everyone around him would die by being overwhelmed by too much bad-ass.
Anyone who denies the man is the biggest bad-ass in gaming, heck even outside of gaming, of ANYTHING, is delusional and should actually meet the Duke sometime.