I would like to nominate Jon Ericson.
He is one of the top contributors to this site so far in terms of reputation. He has asked and answered many questions with detailed and technical answers, as well as actively participated in the Meta discussions, especially about inciting conversation about the scope of what is and is not on topic for this site.
[Jon Ericson writes]: I am honored to be nominated and grateful for your many kind words (not just here but in the comments to my answers as well).
There are a few things I'd like to clear up, however. I'm not a moderator elsewhere. My Top 5% rating on StackOverflow is less impressive than it sounds. I participated heavily during the beta and suddenly stopped. Meanwhile my corpus of answers continues to receive reputation while new users (many of whom ask one or two questions before leaving forever) are added. My pattern of participation early followed by complete absence continued in the Philosophy site.
I also have serious issues with the moderation system on StackExchange. I'm reluctant to see questions closed to the point of potentially damaging a site. I don't like the chat system (which is more obstinacy since I've never really used it). I don't read or participate in the Christianity or Jewish Life and Learning sites, which is where many of our off-topic questions are likely to be moved. I think "community wiki" is a dumb feature. I rarely use my edit powers since I believe strongly in preserving an author's words.
On the other hand, I am committed to this site and did comment during the definition stage. I have spent much of my adult life engaged in the topic as a hobby. (My "About Me" here sounded pretentious in the cold light of day, so I've changed it to the one I wrote for the Philosophy site. It fits.) When I've been privileged to lead a study, I've had to take on a role very similar to a moderator on the StackExchange site: putting aside my own opinions for the good of the group. Except for the times I wanted to correct an injustice (in my perception) in a particular question, I've never desired to be a moderator anywhere else. But I think I'd like to be one here.
(Oh! I also use an order of magnitude more words than needed at times.)