Osmos for iPhone & iPad

Osmos is simple.  You're a floaty-glowy bubble, squirting around in space.  You can absorb smaller bubbles, adding their mass to yours in the process, while bigger bubbles can absorb you to death.  In a representative round, the goal is to "become the biggest."  Off you go, absorbing bubbles to get bigger, which allows you to absorb larger bubbles, and so on ... and then you look up and an hour has passed.

The physics are great, and the gameplay is super smooth.  But the other winner is the soundtrack -- fricken excellent on headphones -- transporting you into a world of groovy bubbling grooviness.  The replay value is excellent .. so if you don't have a chance to listen to a level's music the first time through, you'll have plenty of other chances when you come back for more.

Super Meat Boy for PC

There's a section in the Bhagavad Gita about a million deaths that are fated to happen, right?  Super Meat Boy is like a pre-battle meeting with Krishna, if Krishna was a devilishly difficult platformer that packs in nods to other games, other game makers, and other gameplay styles at every possible spot.  It's an epic of game playing.  You'll find yourself gasping "argh" as you die just millimeters from the end of a level, only to smack the keyboard and start the level again.  Just one more and you'll get it.  Sure...  Keep your RSI braces handy -- you won't be able to stop playing this one.