Tim's visiting, so I'm actually playing games. Niddhogg 2 is hilarious and fantastically weird. It's a duel game in which one hit kills the opponent, then you run as far as you can (hopefully all the way to the goal) before they respawn and kill you. And vice versa for your opponent, who's trying to get to a goal in the opposite direction. It's a wonderful combination of tag and something like Bushido Blade.
Ultimate Chicken Horse is also great. Each round, every player places an obstacle in a side-scrolling level then everyone tries to traverse it. Wackiness and difficult accumulates. There are hilarious deaths.