Well @sixnineanon is 6'9 and although that means he is a foot and 3 inches taller than me, I'd still date the fuck outta him. Generally if you're 6'10 or more is my cut off cause I LOVE extreme height differences.
I had a thing for a guy who was 6'4 for quite a long time, and a guy who was 6'3 as well. Though I thought their height was attractive, it was a little annoying when it came to kissing. Not that I make out standing up ALL the time but it's nice to have that option, and making out with a guy who is almost a foot taller than me (I'm 5'5) hurts my back after like a minute. So 6'5 was what I chose. I couldn't handle any taller than that.