QWOP
You control a track runner to get as far as you can with Q, W, O, and P which are the left/right legs and (I believe) thigh/calf motion.
It's very difficult, failure is entertaining, and success feels great.
My 9-month-old is just starting to get into assisted walking, and I always compare his attempts to QWOP. Only a couple people have gotten the reference and it makes me very sad.