The Optimist: Fighter, being so child-like and optimistic, contrasting black mage, they even came in together at the start of the story)
The Realist: Red Mage, with leadership tendencies of thinking up plans and trying to actually get the group to complete missions and what not. Can also be considered an Apathetic, what with caring only about stats.
The Apathetic: Thief, who only cares about money. Like Red Mage in being uninterested in getting between Black mage and Fighter.
Grim Trigger has Tage as the realist, Hunter as the optimist, Proxy as the cynic, and Lodin as the apathetic.
Homestuck: John is the Realist, Rose is the Cynic, Dave is the Apathetic, and Jade is the Optimist.
The Order of the Stick gives V (the Cynic), Elan (the Optimist), Roy and Durkon (the Realists), and Belkar (the Apathetic). Haley is initially also Apathetic, but eventually becomes a second Cynic (though a street smart one, to contrast with V's book smarts).
Rumors of War: Nenshe (the Cynic), Elysia (the Optimist), Illyra (the Realist), and Occela (the Apathetic). This despite the attempts of several main and supporting cast members to make a cynic of Elysia.
Something*Positive: Vanessa (the Optimist), Peejee (the Realist), Aubrey (the Apathetic), and Davan (the Cynic).
The Word Weary: Jason (the Cynic), John (the Optimist), Sam (the Realist), and Yorick (the Apathetic).