Distinct Spell Reactions
All spells make the same reaction once cast: a jet of light comes out of the wand and spins in a circle for a second or 3 before it is deemed successful or not.
Would be really cool if each spell produced that which it is trying to accomplish, to mention a few:
Augumenti- (no light) a stream of water that douses the fire
Arresto Momentum- (no light) a see through net that stops the pixies etc.
Bombarda- (no light) small explosion
Expecto Patronum- Silver shield (or the shape of an unidentified beast- or an achievement can grant a selection of beasts to choose from)
Incendio- red and orange swirling flames
Protego- a clear expanding shield