Well, you can do some pretty annoying things. Focusing basicly on arena here. If your talking a straight up 1v1 fight I have always been a fan of not standing still unless my opponent is snared down.... that means im only casting CoC, AE, Nova, Fireblast and Icelance while running around like a nut with boar's speed on boots. It totally depends on the matchup however. Believe me, you can mess up a healer without any trouble... C/S the first heal, hit them with an instance cast... spellsteal usually is some good, then cast polymorph on them immediately. they won't get a heal off...Hit the other bad guy your partner is on a couple times just before the poly breaks, cast icebolt, then lance lance lance lance to stack up your +crit and then counter, poly etc each time its up... eventually hes still ok on health from the poly heals but is totally out of mana. You just pop a gem or your lovely channeled mana regain. and by that time his buddy is dead.
Any 1v1 type combat is well served with spellstealing everything followed by a polymorph and then channel mana regain while they are polymorphed... and they just start the fight over basicly, except now you have all your buffs, plus all theirs.
Ice elemental iceblock has to be the most annoying combo for another class that is out there.... especially if you watch to see if they untarget you to hit the elemental out of frustration and immediately drop block to hammer them again.
A macro to cancel iceblock on first keypress, blink on second key press is great if you you swiftly swing your mouse as you hit it. You blink off in a direction before they can tell what direction your facing... gives you time to go invis if you want sometimes before they see where you went to... or even to bandage before they figure out where to turn to face... (obviously, after the blink, it works best to duck around or behind something bettween the two of you..) This is best served with ice-elemental up so they have a friend to keep them company (and keep them from eating/bandaging etc.
If you are talking about freezing your opponent with nova, (assuming they are chasing you, run backwards suddenly while they are on ya... now your behind them and they are frozen.... once it breaks and they turn to come at you again, just Cone of Cold right in their face then blink through them and then either spin and hit em or keep running, cause they are not gonna catch you after that if you run along.) But anyhow, you were talking about a SPELL not tactics to really do some good.... I think we probably have the tools there already.... more tricks is probably best served by adding in a specialty trinket, using racial abilities (escape artist) popping a potion (cure poison, freeaction, swiftness etc) use trade gear... frost grenades, nigh-invulerability belt, Gnomish Shrink Ray on a meleer, etc. Stuff like that.
I would settle for them fixing frostbolt so the freeze effect procs right.