Loremaster - For me it's a toss-up between Kodiak and Zeni for all-time best. Both very good tactically (even without the gems)
Mage - Best all-time was Jhor, hands down. I wasn't around to see Fist reach full maturity, but he's in the running as well.
Knight - Another toss up between Maleki and Threap. Although I'd give Threap a slight edge just because he was far more vicious.
Ranger - Wotan without question and I'd place Pahn as a very close second. Both used the skillset beautifully.
Theif - Gotta give props to Narissa. Best trapper ever.
Sorcerer - The most outstanding in (my) memory is Huzow. Of course, I was but a cub when he was most active, but I remember him being mark everyone wanted to meet.
Bard - No doubt here: Babidi. In fact, I would throw his name in as arguably the best all-around fighter in Avalon history. Granted he was a sick, twisted sadist, but he mastered every profession he played and did so well. I learned a lot from him (being his personal chew-toy for a few decades helped me perfect my defences)
Animist - Gotta go with Lammy now and then. Always willing to put her neck on the line for another's life. Quite admirably a true healer. Also, shout-outs to Zilveren, Maudeeb and Krayia.
Sorry I cannot comment on the youngins. I don't know many of them at all and they're too small for me to be messing with.
Written by my hand on the 17th of Leaflost, in the year 1197.