"Uncharted 2" is an excellent game. One might even say the best exclusive PS3 game ever. In fact, yeah, I'll say that. Best ever! With that out of the way, I managed to capture a video of two of my favorite unlockables in the game, which allow you to play as "Doughnut" Drake (familiar to fans of the first game) and Sir Francis Drake in the single player campaign.
Worth noting that these two unlockables are viewable from the menu right at the start of the game, so I wouldn't call them "spoilers," per se. They also have nothing to do with the storyline whatsoever, and I've picked a point in the game that's completely bereft of story, so you're fine there, too.
Anyway, to unlock the two models you have to play through the game normally. Once you complete it, you can then go back and replay different levels using bonuses purchased in the in-game store. Two of these items are the "costumes" featured in the video. As a cool touch, you can actually play higher difficulty levels than the one you completed the game on and still use the unlocked costumes. (Cheats like infinite ammo and one-shot kills are deactivated on higher difficulty playthroughs, though.)
For those outside of the country that can't view the video, here are two shots of the unlockable costumes: