I need a good comeback.... help me please?

So this guy in my cl, he has an obvious crush on me. As in, he takes my stuff so I will have to walk across the room to go get it from him, and randomly grabs my arm whenever he feels like it. He also stares at me for minutes on end, sometimes he winks when I look at him. I don't really like him staring... and I can't think of anything witty to say to him when I catch him staring! All I can come up with is "why are you staring at me?" to which he responds "I'm just watching" What do I say? Something witty and smart alec, but not rude. I don;t know if I have any return feelings, so I don't want to burn that bridge, but I don't want to lead him on untill I know. Help?