I'm with sage. I've used the lesbian line before, I've given fake emails, and I have also tried to use the engaged one - I have a diamond ring on that finger.
Basically doesnt seem to matter what you say, a drunk guy will dispute it.
I've even said I only just got out of a bad relationship and i wasnt interested in guys right now (yup, the totally honest line) and it STILL didn't work.
I'd say my line, if he keeps up just say 'look, I am flattered, but im not interested at all.' then leave. It annoys me that we have to move tables, leave the club or whatever to get someone to leave us alone sometimes. So silly