My brother is twelve and I bought him a build-it-yourself robotic arm kit for $40, but if he gets frustrated easily that's prooooobably not going to help you haha. My brother is a little scientist and very nerdy so this was great for him.
What type of video games does he play? Maybe you can get him a cool looking controller if he plays XBox or PS3. Does he talk to people online while playing? Maybe a neat headset, I just bought my cousin the PulseWave 2 headset because I didn't want to buy him a video game or gift card again this year. It had good performance reviews and it also lights up and vibrates, which I figured is cool factor gold for a 14 year old. If you wanna go that way, make sure you know what he plays on (PC uses 3.5 input or USB, XBox has it's own special connection type, and PS3 uses USB or bluetooth).
Do you know specifically what games are his favorite? A bunch of games have their own toys or apparel. Call of Duty: Modern Warfare is my cousin's thing, so I've gotten him a poster before. Thinkgeek.com has some really neat stuff that a 12 year old might think is cool that isn't video game related (Like a shirt you can play guitar on).
And that's about all the help I can offer you! When I'm really stuck for presents, I just start browsing websites and hope I stumble upon the perfect gift.
Hope you find something!