I am about to write a scene involving a magical duel, and it occurs to me that just about all the forms of combat damage have been done to death. Fire, electricity, wind, poison gas, summoned monsters and cold are fairly common; acid somewhat less so.
In a brief bit of brainstorming, I came up with gravity control, ionising radiation and weaponised dimensional vortices - none of which I've seen in fantasy works although they may be in something I haven't read. Any more? Evil ideas are welcomed.
Sounds pretty standard fare for you're typical magical stuff. (Dr. Strange springs to mind)
Trudi Conava did a good job of magic battling in the Black Magician series.
Old Potter had some good scenes too (much as it pains me to say it)
"The Raven" duel made an impression - I was young - pity about the camp aspects but the Carloff Price scene was most enjoyable at the time and at the forefront of special effects too.
So, for something new.
I'd resist acid attacks - Far too dodgy in todays world. You wouldn't want to be quoted come the next attack - Plus it's hardly magical.
The real problem - is not finding the attacking magic, but the defensive magic against it.
As in Rock, Paper, Scissors.
A big hole in the HP tale is the lack of an anti curse against the issuing of the killing curse. If all you have to do is say the words and point your wand and someone across the room is dead, it doesn't leave a lot of room for the hero to guard against it.
Sneak out from behind a tree and say the world and your enemy pops his clogs.
The the Cruxious curse and HP shielding against it was better.
So we have:-
Fire - Water - vacuum, damping gas.
Water -fire, vacuum, drains/holes.
Poisonous gas, fire, water vacuum, window blast.
and so on.
How about:-
Projecting into solid matter - guarded by the attackee realising and crating a bubble around himself.
Sudden appearence of holes/earthquakes guarded against by levitation.
Similar to water being plunged into at depth guarded against by the bubble again.
Wind v Wall building
Energy beam v mirror
Insect attack v poisonous gas, bubble.
Tossed into space v bubble, coming straight back.