Lili Bykerk made a pretty cool portable 2 player arcade console.

This controller uses a Raspberry Pi running RetroPi to run the game ROMs and a Teensy 3.2 to act as a game controller using a modified version of the USB Joystick code. The controller also features an HMDI port to plug into your TV as well as 2 USB ports in case you want to plug in your own arcade controller rather than use the 2 that are built-in.

Lili put together a great Instructable on the project that details how to build your own and also provide the code for the project.