If there was any weapon you could have from any game, it has to be the portal gun from the game of the same name! Well these guys have a fully operational portal gun and are not afraid to use it either! This is one of the best portal gun fan videos I have seen, the effects are simply brilliant especially the scene where the guy falls through the portal on the floor!
According to the maker of the video, Jason Craft, he said;
My interpretation of what a real POrtal gun would be like if one existed. Based on the video game, Portal. I tried to match the game as close as possible. This was the most challenging project I have ever undertaken, consisting of 3D tracking, seamless camera cuts and 3D camera projection. This started out as an experiment since I didn’t think I could even pull it off, if I knew it would’ve turned out as good as it did I would’ve put more of a story behind it. O well, it makes up for in Visual Effects, ENJOY!
Source [Geeky Gadgets]