Now there's love, and there's making your girlfriend an incredibly detailed replica of the Aperture Science Handheld Portal Device (ASHPD) gun from Portal. Planned from game screenshots and constructed out of such mundane items as an acrylic plunger handle, it lights up, has articulated claws and will generally go perfectly with said-girlfriend's Portal cosplay costume.
In use, the barrel of the gun lights up blue and orange, while red LEDs light up the three prongs. Rather than leaving it immaculate, they've then artificially aged and added a few blood splatters to the casing, so that it looks as though it's been around the testing facility a few times already.
There are plenty more photos to be seen - from a lot of different angles - at the Cosplay.com forum page here. There's also plenty of background into the construction, together with a gallery of in-progress shots.