At the risk of sounding like I live in the past. The three greatest trolls are:
Skin of Evil
Granted there are many other great trolls, but the three above are the ones I consider the Greatest EVAR!
Maybe if we had a top five I could add RobL and MsScribe. Of course, we'd actually need a top ten (or maybe even twenty) to really reflect a good sampling of trolls. Because with even five, trolls like JillianBacardi and Sarek (TK's longest running troll EVAR!) wouldn't be on the list.
Note: I don't believe Red Quacker ever posted on TK, and I'm reasonably sure MsScribe never did; though with MsScribe one cannot be altogether certain about anything. But I felt they both deserved a mention.