Sure, everyone and their mother has made a custom Portal gun at this point, but the fine folks at Hackaday have raised the bar into the stratosphere. The floating Companion Cube effect was accomplished by ripping out the magnets in a floating globe, and the cube itself was created to proper size and weight specifications.

The gun itself is not custom, however - it's store bought. The process of creating the Companion Cube and applying the magnetic housing to the Portal gun itself is pretty interesting, all of which you can check out in the video above and through the source link below.