Portal: Survive! is a live-action short film based on the Portal game, and its tie-in comic Portal 2: Lab Rat.
Portal: No Escape
Check out this excellent short film based on the Portal video games, called Portal: No Escape.
Counter-Strike: Global Offensive - Trailer
Valve show a grittier more realistic use for Source Filmmaker with a trailer for Counter-Strike: Global Offensive.
Valve's Source Filmmaker
Valve have announced the Source Filmmaker, their tool for creating animated films in a very intuitive way.