A pretty scuffed version of CSGO for the browser, online.
App is live at: https://3dfps.glitch.me/
Server is hosted on http://herokuapp.com/
Original: https://github.com/TheCoder5550/3dshooter
Feel free to fork and make changes, i can see potential, like maybe you can make it Like minecraft. :D
[note you'll need a new server]

Edit: i noticed that people said the join button wasn't working. To solve this issue, enable Javascript in settings.