I would say anything superhero would be a good bet. Also, you can never have too many nerf guns, and they have good ones in that price range. My boys have also always loved Star Wars & Legos, but I know not all kids do.
I would also say that the Target gift card (or even a crisp $20 bill) is a good idea as well. My kids always used to get presents at parties, (and then there are always duplicates that need to be returned) but I've noticed as they get older that they're getting more and more gift cards or cash, and they love spending it. Last year my 10 year old made out with about $140 in gift cards and cash, and was able to go on a shopping spree. He was grinning from ear to ear the whole time! If you know any other kids attending the party, call their moms and see if they want to go in on one big present or gift card. 3 kids giving a $50-$60 gift card allows the birthday child to get something really cool. When I give a gift card, I usually buy one of the really big Hershey bars and wrap it so that the child has something fun to open, and then tape the gift card to the front.