After doing some research, I found out that this Portal Gun comes from a game called Portal 2, a first person shooter developed by Valve (creators of Counter Strike), where you solve puzzles by transporting yourself and objects through flat areas of space. Apparently it is a very popular game, never played it. Why I am highlighting this is because the gun used in the game was hacked to do a levitation of a cube object, all very simple to do by yourself, and very cool for a display. Take a look.
http://hackaday.com/2012/10/11/hackadays-portal-gun-actually-levitates-a-companion-cube/