Nidhogg by Messhof
Don’t judge a book by its cover, especially free indie games. Nidhogg was commissioned by NYU and was an instant hit for public gaming. Nidhogg became a game best played in front of crowd.
At the heart of the game, two players face off in a fencing match and must kill their opponent to progress through the level. However, the opposing player only dies for a few seconds and quickly responds, never halting the action. The art is simple and the graphics outdated but the gameplay is addictive and the first time seeing a live Nidhogg fencing match is like being baptized all over again.