An open-source Phantasy Star Online server for *nix
Pontoon in c - source code and header file
Android, DOS, FirefoxOS, Linux, MacOS and Windows all in one..
Multi-platform game engine similar to old Megaman with a stage editor
Single-/multi-player card game Mau Mau (similar to UNO®)
Invaders like game, written in Python with Curses... :)
A Bash Front-End to FCE Ultra