ev.io

ev.io is a futuristic Halo-esque first person shooter in the browser. Play private games with your friends or play ranked public games. Earn in-game currency based on your performance to purchase skins and other cosmetics.
WASD to move. Right-click to aim. Right click to zoom. Space to jump. T for melee. G for grenade. (All hotkeys can be changed/configured in settings.