He won't stop flirting with me?

A guy I like at work has been joking around/teasting/flirting with me for the past 8 months at work and around July I was seriously thinking that he liked me. Turns out he went for another girl at work who is now off a few states over in college. He still continues to flirt with me and at first I was just like, ok whatever, I'll play along but now because I know he doesn't like me it's really bothering me.

I've asked advice on this before here and I've tried it all. I've ignored him, I've told him flat out that I don't want to joke around or have him bother me, I've been just downright mean, when he says something to make me laugh I just stare blankly at him like I give him the "you're an idiot" look. He told me that for once he wants to walk over to the counter and me be smiling at him, I said that's not going to happen and he said if he tripped would I laugh and I starting laughing and said yes.

I've told him to go away, I've tried to basically making it clear that I don't have a crush on him (if that's the reason he picks on me--to feed his ego). But he won't stop. He says he can let up on the throwing of napkins and stuff at me but he can't stop the tickling. What do I do? He's a nice guy but I'm really having a problem with him still flirting with me. I've asked him if he bothers anyone else this much and he says "no", I ask why me and he says "because it's fun".

Am I just supposed to be like you know what I like you and you joking with me isn't helping because I know you don't like me? (So it eventually turns awkward and he goes away?) I can't get over the guy if he continues to do this. I can't change my work schedule because of school. I have to be "nice" to him because we work together. He's not generally annoying or anything, he's only annoying me because he flirts and doesn't like me.
He won't stop flirting with me?
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