I would prefer not to get cash as a gift because I know that I'd probably end up banking it or spending it on upcoming birthday gifts. With a gift card, you basically have to get a gift for yourself.
ANYWAY...if you're thinking about getting your cousin a gift and you really want it to be a game, when I heard "not into PC gaming for long" and "likes MW2" maybe you can get him the Orange Box. Sure it's old school but TF2, man. It's not that expensive and would make a nice gift-y accompaniment to being taken out.