Ricochet

Ricochet is a first-person shooter multiplayer video game. It was developed by Valve Corporation and originally released on November 1, 2000. Ricochet is an official modification, and is available through Steam for purchase; however, it is free for those who purchased the retail version of Half-Life prior to the release of Steam.

Ricochet's gameplay notable is for its apparent simplicity, inspired by arcade games and platform games in both concept and design. Players jump between neon-lit platforms suspended above an abyss, and shoot disks at one another, trying to push the opponent off the platform and into the depths.

Source: Wikipedia