I too love this bundle. Pretty awesome that the three charities are Watsi, Child's Play, and EFF.

The games are all very distinct from each other and top notch. My three favorites:

Fez: a perspective-altering puzzle platformer. It's cute, clever, and well designed.

FTL: a real-time starship crew management game, where you assign people to stations and target your opponent's systems. You fly through randomly generated galaxies and have random encounters. Super replayability.

Mark of the Ninja: a stealth-action ninja platformer with very high production values and multiple paths to victory.