Galaxy Forces V2 is a classic 2D side-scrolling game inspired by Gravity Forces on Amiga. It allows up to 8 players, involves shooting enemy space ships and either transporting cargo, point races against opponents, or shoot-everything scoring. There are 50 official levels and a map editor, and it runs on Linux, Windows and Mac.
RPGboss is a 2D role-playing game engine and application designer. It requires little programming logic, comes with a map editor and tiles. It allows custom screen sizes, side battles, defining map events and interactive dialogs, JavaScript usage, items/inventory, in-game menus, managing scores and skills, animations, characters and enemies. Completed games can be exported to Windows, Linux and Mac binaries.
Seagull Soup is a simple shooter game with joystick support. It utilizes SDL and works on Linux, Windows, BSD, Mac OS X. According to the source code there are seagulls, cannons and a whale involved.
The Last Mission is a remake of a classic OperaSoft game. It's a side-scrolling shooter game about a robot send back to earth to inflitrate and escape the enemy robot base. It's reimplemented in SDL, available on Windows and Linux, and the OpenDingo plattform. It uses classic 4 color CGA-esque grapics, but in contrast to the original 8-bit game features Facebook and Twitter integration.