A multiplayer 3D game a few friends and I made in 48 hours for the Node.js KnockOut 2011 weekend competition using only HTML5 (no plugins at all).
Outburst is a 3D real-time multiplayer game that combines the best of a tower defense and a “twin-stick” shooter.
Full-screen WebGL. Animated 3d models. Seperate walk and aim directions. Multiple weapons. Spread and recoil simulation. Mouse cursor animates with machine gun. Chat. Twitter integration. Ammo in HUD. Dynamic camera with zooming support. Pre-loading of game assets when on front page.
Clients employ client-side prediction for their own state to fake responsiveness. All movement and shooting logic is shared between client and server for this. The game client itself is 100% vanilla HTML+CSS+JS.
More info about the entry can be found at http://nodeknockout.com/teams/aranja