From time to time there are games that seem to scream "Make me into a movie". Portal isn't exactly one of those although anyone who's played the either game will have more than likely thought of quite a few uses for a portal gun if it were a reality.
The closest we are going to get to the real deal right now unless Area 51/Groom Lake has some secrets up its sleeve is the short film below that does a marvelous jump at translating Portal to live action.