Check out Seecolonslash for what is possibly the funniest gamer t-shirt I've seen all year. I'm just regretful it's too late to get them for Christmas or I would have knocked many a gift off my list. Also, the site is open to people who need an outlet to sell nerdy stuff, so this is your opportunity to sell your homemade gamer fashions. Go for it! Personally, I'm still waiting for someone to make a long clutch bag that looks like the NES controller (hint, hint.)
Thanks to Josh for a great tip.