Line Rider

Line Rider! Probably one of the best flash-based games ever. Seriously. If you have a Wacom tablet, this is the game for you. Here's the gist. Draw a line, press play, and then a little guy on a sled will ride the line. He(she?) can do loops, face grinds, back grinds, jumps, etc.. To see how far people have taken this, see here. Line Rider