Jumper!
This incredibly simple and functional game stole my soul when I was linked to it a few years back. It's basically the ultimate skill platformer. Like Mario you transverse through levels trying to reach the end, but unlike Mario there is levels in this game you will die on more then 1000 times, when you finally nail them the relieve and excitement being almost orgasmic, although of course the next level is no less difficult then the last. There are two more titles in the series but you really should play through them sequentially, as there is a story. He's a screen shot for how to do level 2-1 since I couldn't find a screenshot that didn't have help lines drawn in, we used these things to show people who couldn't figure out a level how it was done originally.
Jumper Two!
Jumper: Opposing Forces
This game is so basic, but it's still like crack, enjoy!