Playing Portal, admiring the depth of the puzzles, I couldn't help that feel the portal gun would be a really fun weapon to have in a combat FPS. You could set up some really elaborate punishments for your enemy. For example, stick a Portal under a Strider's leg...it'd just happen to come up and impale your enemy through a second portal in the wall. At the same time as catching a strider in a hole. Just thinking, maybe in a multiplayer game, this could be really fun to use.