This life-sized portal gun from NECA Toys is an official licensed product from Valve’s award-winning game, Portal. With just 5000 of these produced, it’s very very limited. If you’re looking for any seller, chances are you’ll find them on eBay with selling price 3 to 5 times the retail price.
Here’s a nice user review from itburnswhenithink.
The Portal Gun unboxing video from GamespotUK.
Here’s a fan video of how it works in the game, replicated in real life.