Line Rider Game
I don't quite know what makes this "Game" so fascinating, but I find it to be lots of fun. You draw a line from left upper to right lower on the screen, then click on the triangular play button and a little guy in a toboggan slides down the line. If it's too steep, or the bumps are too high, he crashes in a fairly spectacular manner. Give it a try!
Hat tip to Blinkerfluid for finding this!