What is Nidhogg? It's an orange man vs a yellow man. It's a fencing football game. It's about dragons and it's the winner of the 2011 Nuovo Award, which means its great at being experimental/artsy/peculiar.
It's an abstract fighting game and a lot of fun (proven at the four-minute mark of the video at that link).
Nidhogg is being acted out for you, right here in the video atop this post, by its creators, because I asked nicely.
We shot this backstage last week at the Game Developers Conference. Congratulations to the game's creators, Mark Essen and Greg Fox, on their Nuovo. The game will be out... someday. Check the Nidhogg website for updates.