I always go into pay negotiation with the obvious trump card -- I'm good, so I'm worth it. I don't remember ever being denied. I do remember going in three months later with, "I'm better than this pay raise." That didn't work, but just once. lol
Of course, it helps that I have a head for numbers, so I can generally prove the company got more than a 1% increase in profits in the last year. (The only time I couldn't prove that is when the company didn't. I still got a pay raise of more than their increase in profits. I'm not a profit. I'm an asset. lol)
Have you tried, "How much will it cost you to find someone as good as I am if I quit" yet? It works. And notice, I never told them I was quitting. I just asked the obvious question they're thinking when someone does threaten that one.