Hey, a topic I feel at home with.
For me, definitely Chioda. When I ref in the indies, I try to copy his general mannerisms from the devil horn two-count, and the putting-your-foot-down attitude. I was also a bit of a fan of Brian Hebner, from which I copied the armband look but that's more because I get sweaty during matches. And I try to watch as much Tommy Young as possible as he always paid attention to details.
And I love, love, love that the WWE refs recently started checking shoulders with that little hand slide during pins, and generally treating matches as more of an athletic contest between two wrestlers rather than Sportz Entertainment segment #2-B. We haven't seen a ref bump in a high-profile match, haven't we? That is good. So very good.