Favorite mage? It was the Wizard until it got a lot of hate from people who hated the Tower. That (not the changes to WT or anything, just the general feeling of hate) really killed my desire to play it.
I haven't played a lot of Mages, but of the ones I've played some... probably the Straywood Beastmaster. I can make a pretty straightforward plan without a ton of thinking about technical / timing / synergy things... just keep casting animals, and get ready to melee. (My brain hurts if I have to think too much.) Mine might not always be the best strategy, but I know it won't be the worst....
OK... my favorites, using another way of judging... either the Priestess or Wizard, since they both channel 10 to start and have an innate spell ability that provides options during the game.
Best mage? I tend to lose equally with all of them.
What mage do you least enjoy playing or paying against? Any that zot plays, since he's about the only one I've really played... and since he nearly always kills me. I guess if I really had a favorite Mage, I'd also have a least favorite, since it would be the one who does best against my favorite....