Line Rider - Amazing!
A while back I did a post on an addicting little game called line rider. Basically you draw a line with your mouse, then a little man on a toboggan slides down the line, going over the bumps and so forth, and if you did it right, he won't crash going down the hill.
Some amazingly talented folks have not only drawn some incredible "tracks" for the guy on the toboggan, they've even added scenery and sound tracks!
Here's a really good one saved on Google Video.
If you do a search on Google Video for Line Rider" there are a bunch more you can watch.