ColinR was one of RationalWiki's founders, with Trent as the other founder. We say "was" because he vanished without a trace after making his last edit ever, which was ironically a post on his talk page that read "Thanks. Hopefully now I'll actually contribute to the site." To be honest, he didn't really do that much.
UPDATE: In possibly the longest absence to come back from, lasting over a decade, ColinR has returned.