Nidhogg

Nidhogg is a fast-paced two-player dueling game where two players sword fight in a side-scrolling environment. Players can run, jump, slide, throw their swords, and fistfight. The game has a pixelated aesthetic. The release version of the game includes new mechanics like dive kicking, wall jumping, ledge climbing, and crawling. The player continually pushes towards one side of the screen, such that the player is permitted a few seconds to run towards their opponent's side while their opponent respawns after dying. The player-character's sword can be held at three different heights.

Source: Wikipedia, "Nidhogg (video game)", available under the CC-BY-SA License.