Not every genre is suitable for multiplayer mode which is the core requirement for an .io game. The most obvious ones are already implemented. Nevertheless from time to time we discover absolutely insane gems!
s0urce.io is a hacker simulation and it's done with great attention to the details. Built using jQuery & socket.io, hosted probably on a single server instance.
So what is this game about? You've got the list of players (opponents). We need to select one and begin hacking him through one of available ports (A,B or C) by typing some commands into the command line. Hacked player gives bitcoins that can be used to buy new servers at the black market. You should be aware of other players trying to hack you at the same time! Upgrading firewall allows to decrease vulnerability of your servers.
This io game is a pure fun!