I bought the Humble Indie Bundle 2 yesterday. Five games, pay what you want- AMAZING Deal. I think I will buy one for my friend as well.
Braid- This game earned rave reviews when it was first released. It's a FUN puzzle-platformer with a great time manipulation mechanic. I fail to see how it changes your world, (haven't finished it yet) but it's worth playing for sure.
Machinarium- What? A commercial Flash game? Madness! Calm down, it's actually quite good. Interesting art, well thought out puzzles, and some interesting height-changing mechanics all add up to be one of the best Flash games you will ever play.
Cortex Command- This is actually not finished yet. It's sort of like Command and Conquer meets Scorched Earth meets Mega Man (roll with it). It's very much a rough work in progress, but it's worth checking out for the amazing "pixel physics" engine, which creates the most advanced 2d Physics you will ever see. If you are willing to meet the game on it's level, and look into the mods, you might find it to be fun, but it's definitely my least favorite in the pack.
Osmos- I already had this on iPhone, but it's nice to get the PC version as well. It's a calm, dreamy game about eating cells, but it can get frantic if you choose to do so.
Revenge of the Titans- This is apparently a new one. I can't wait to see how the reviews turn out. I gotta say, for me this was a complete surprise. I yawned when I learned that it was a tower defense game- not my favorite type. Instead, it turned out to be one of the most epic tower defense games I have played, more arcade RTS than tower defense. There was a level early on that gave me massive headaches, but I felt so satisfied like no TD game I've played before after I finally beat it.
Grab this deal now, it only has a few days left.