With Halloween fast approaching, ThinkGeek's new Miniature Replica Portal Gun ($59.99) is going to be hard to resist. It's got appropriately colored LEDs, a working trigger, and movable claws. Parents, think about how much candy your children can get for you while repping Portal 2; just send them to bed before they eat it all.
At 12" long and approximately 5" tall, this gun is also the kind of collectible you could reasonably keep on your desk when you aren't chasing around cats or otherwise making a fool out of yourself. Seems like a fun purchase if you haven't already overdone it with Portal merch.