Lego. Make sure it's the small kind so that he'll choke on it!
hmm maybe a big truck of some kind? that or a big plush doll. I got my cousin a big triceratops plush for his 3rd birthday (it was probably a foot long and half as high). I would get something simple, really. Is he walking? You can get him one of those bouncy-ball mowers or something to help him learn. Otherwise some keyboard with animal sounds or something would be cool. The coolest thing you could do is get him something that he can interact with on a simple level.
Depends no his age, but you could buy a plush doll with a matching shirt or hat, maybe. Like get him a monkey doll and buy him a monkey hat from the dollar store or something.