Seriously, boxes.
Any gift you get him, the box it comes in will be at least as entertaining, if not more so.
Does he show any signs of a specific interest?
DS was (still is) huge on cars, so I got him a multi-storey parking lot thing with a lift and ramps, and he LOVES wizzing the cars down the ramps.
Seriously, at two, they're still just all about making a mess and getting themselves into ridiculous situations, so I'd just generally go on a hunt through google/amazon for "toddler toys", and see what catches your eye.
Xx