Not content with a simple Portal Gun prop, YouTube user trpchakai has constructed an intricately detailed and extraordinary puppet of Wheatley from Portal 2. It's certainly an impressive way to set yourself apart from all the other cos-players dressing up as Chell.
The entire creation process has also been helpfully chronicled on her blog at Furin Cosplay. He also quotes ten different phrases from the game shown off to great effect in the video above as his puppeteer matches his mannerisms almost exactly to his character in the game. I think we can all agree that Valve has some incredibly talented fans.