Supertux is basically a Super Marion clone, with simple graphics but fun gameplay. Although the game is fairly easy it can be beaten in a couple of hours, by anyone. I always found the game quite fun and the reason it's mentioned here is that there is a version out for the PSP.
Since some of you might not be familiar with the title I posted a video of the gameplay, please note the gameplay is greatly speeded up.
If you like what you see the PSP version is available HERE