Here’s the 2nd edition of Tight Ass Tuesday!
Team Fortress 2 (commonly abbreviated as TF2) is a free-to-play team-based first-person shooter (FPS) multiplayer video game developed by Valve Corporation. It is a sequel to the original mod Team Fortress based on the Source engine. It was first released as part of the video game compilation The Orange Box on October 10, 2007 for Windows and the Xbox 360. A PlayStation 3 version then followed on November 22, 2007. The game was later released as a standalone package for Windows on April 9, 2008, and for Mac OS X two years later. Team Fortress 2 is distributed online through the Steam system, while retail distribution was handled by Electronic Arts. On June 23, 2011, the game became a free-to-play title, supported by microtransactions for unique in-game equipment through Steam. Wikipedia
It is available for both PC and Mac and can be downloaded here.