The Gears of War mod team who were trying to make a Terminator shooter have switched their efforts over to UDK, and the results are pretty fancy. You can check out their video, below, or actually go and play the thing by grabbing it from their Moddb page. I’ve not had a chance to look at it yet (Alien Swarm to play) but you won’t need UDK installed to make it work, so why am I mentioning it? A mystery. Also there are some fiddles in the install instructions, so pay attention.