We just had a thread on this very topic: http://www.mothering.com/discussions...d.php?t=376188
It all depends on the child's special interests and developmental stage. I'd recommend wooden toys/puzzles over electronic toys that may hurt his ears if he has sound sensitivity. Two of the best gifts my son ever received were a box full of random office supplies (highlighters, stickers, post-it pads, hole puncher, etc.) and a lunchbox full of Hot Wheels cars.