Let's say you're a Valve super-fan. I know I'm reaching somebody out there with that label. And you want to buy yourself something nice. Something Valve-related that nobody else has.
Forget lithographs or coffee mugs. You need to get this. It's a replica Portal Gun signed by the development team. All proceeds go to charity (Child's Play). And at time of posting, it's on eBay for a surprisingly reasonable price of $760.
Considering the worth of something like that to super-fans, and the place your money is ending up, that's a steal.