Nidhogg is a side-scrolling two-player fighting game by Mark "Messhof" Essen. Players duel with swords in a pixelated environment. The game was commissioned for the New York University Game Center's annual multiplayer show, and was revised and demoed at private events over the next four years before its final release. It won Indiecade 2013's Game Design award and the 2011 Independent Games Festival's Nuovo award.
Source: Wikipedia, "Nidhogg (video game)", available under the CC-BY-SA License.