Valve's Portal Gun

Ok this is semi-unique.
Anyone who's played Prey (what?! you haven't?! get it now!) will know all about those funny dimension-shifting portals they introduced.
So, not to be beaten, Valve have released a trailer for what they call a Portal Gun, which might be used in future Half Life 2 Episodes. The gun does exactly what it says on the tin, ie lets you create portals anywhere you want!
The consequences (and physics-related exploitations) are unimaginable.
If people could trick-jump with humble Quake 3, imagine what they could come up with using this one!

Valve have released an interesting trailer of the gun, in a safety-at-work style video. Enjoy.