I would like to nominate Undo, as he seems very helpful and not obnoxious even though he has a lot of reputation.
Main: http://softwarerecs.stackexchange.com/users/46/undo
Meta: http://meta.softwarerecs.stackexchange.com/users/46/undo
'very helpful and not obnoxious even though he has a lot of reputation'
@gparyani he seems very helpful and not obnoxious even though he has a lot of reputation. On other forums, such as Apple Support Communities, the users with high reputation tend to be very obnoxious. — Compukid16 mins ago
@Undo I support that as a valid reason for being a mod. :P
@Compukid you should edit that into your answer, as not everybody reads all comments (wait, this is a community wiki even... done :). Apart from that, I second what you wrote about Undo: that's exactly what I've noticed about him. — Izzy10 mins ago