For Billy, my soon-to-be-wife's 10 year old Aspie, it is Dinosaurs, bees, the colors yellow and black, his nasty drool, crust, and snot covered stuffed dinosaur (sorry, OCD, and that really bothers me), video games, understanding comedy, and computers.
Fortunately, as a computer professional myself, he now looks up to me as a role model and wants to be a computer programmer when he grows up. I eventually want to start my own consulting company, and if I do, I will guarantee him a job for life.
Oh, and the Washington DC Metro. We went on a vacation down there to visit last summer. Thinking of planning another trip this year, he loved it so much.