SMB (Super Meat Boy) is fantastic. I was just playing a level in the "dark world" (harder versions of the normal levels) and I kept getting a bandaid (hard to get collectables) but it seemed to be glitching out and not giving me credit for it. I said, fuck it, one more time, and blam - it froze up and then the screen flashed "you have unlocked teh internets", hahaha in a 8-bit looking matrix way. Then I was just back in the game - don't know if it did anything.
One of the coolest thing is that it's full of unlockable indie-games characters like the dude from Braid, Castle Crashers, and other games that are too indie for even me. The PC version has different unlockable dudes like a headcrab from Half-Life and the Minecraft dude. Pretty sweet.