Things to try:
Pixorama : Crowd pixel painting
Converter : Fun unit converter
Glitchburst : A co-op top-down horde shooter that runs entirely in the browser. No game server. Every client talks to a public MQTT broker over WebSockets, and one of them volunteers to run the horde.
Computer vision games : Place the blocks in the hole using your body
Countdown numbers game : Solve the answer only using the numbers available to you