Help on getting revenge?

There is a black guy that rides the same bus as me and always sits next to me and you guys know how sometimes you get out of school and you are tired and you sleep on the bus for a little bit. Will if you do know what i mean then that's what i do and he always trow stuff at me and pretends that he didn't so my question is how can i get a good revenge on him without letting him know that is was me?