Well, damn. Three very worthy users in what I presume to be the final round. This is a tough decision. They're all among the best users on this site.
3p - MontanaHatchet. The man who would defend PlayStation from the ridiculous numbers of attacks it was receiving several years ago without even owning a PS3. The mod who was never afraid of challenging trolls and getting them to back down, but who was always fair and friendly to those who deserved it.
2p - Badgenome. One of the most hilarious people I have ever had the pleasure to encounter. This site would genuinely be a much duller and drier place without him. But he knows when to step back and be serious, and when to have a proper discussion, and he's perfectly capable of being funny and interesting at the same time.
1p - RolStoppable. A legendary user, a brilliant thread creator, unmatched in the field of getting people to believe ridiculous satire. He has had some real gems over the years, and even though I think (and have said) that some of his recent threads don't quite capture the magic, the memory of him alone defines this site more than perhaps 90% of the other members combined.
Any of these three would be a worthy winner.