Rare breeds are fairly easy to spot.. they're just what you never see.
Fire Assasin.
Any SS.. period, bear barb, bear,wolf, etc..
Throwing Barb
Hybrid Zon/ Psn Zon
FishyMancer/PSN
Hydra Sorc
Echantress bear, like wut omi said
Fire Druid
..Play around with lots of choices. Although the trick is making them good..
Any unique, rare character will be fun lvling but when you get pwned in every duel... they lose their amusement fast.. trust me
However, godly gear can make most builds powerful with practice since other people arn't used to dueling that rare type.
Good luck in what you choose.
I've always wanted to make a godly Bear/enchant sorc or a Hydra/Enchant bow merc sorc... yet to be accomplished.
Peace