Portal: Survive! is a live-action short film based on the Portal game, and its tie-in comic Portal 2: Lab Rat.
Portal 2 - Perpetual Testing Initiative
Valve are introducing the Perpetual Testing Initiative for Portal 2 with this new amusing trailer.
Half-Life: The Downfall of Evolution - Trailers
Two trailers are out for Half-Life: The Downfall of Evolution, a fan-film taking place in Valve's Half-Life universe.
Team Fortress 2 - ZombiU Crossover (Source Filmmaker)
This Team Fortress fan animation created with Source Filmmaker is a cool tribute to the ZombiU CG trailer.