Team Fortress 2 (Source)
A game by Valve Software. Subject of various competitions on the Polycount Forums.
Tools
Tutorials
Import/Export
Getting your TF2 hat in game as a Physics prop - A tutorial on how to import, setup and export hats for TF2 by Zipfinator from the Polycount Forum
How to EASILY get your item in-game. by larolaro from the Polycount Forum
Texturing
Texturing for Team Fortress 2 - A short guide to painted textures by Swizzle from the Polycount Forum
TF2 Texturing - Making Of - A short guide on how to create TF2 style textures from photos by [iWi] from the Polycount Forum