Buy It: Etsy
Stickers and decals are a great way to show appreciation for your gamer. Over on Etsy, there are a variety of decals you can choose from, for many different fandoms and games. Half-Life items are difficult to come by, so any fan of the classic game would appreciate a small token of your affection in the form of this decal.
The smallest size, one inch, is $.99, and a five inch decal is only $4.99. Decals are made of vinyl and can be used to decorate computers, phones, cars, controllers, or other items.