Well, what in game effects can't you do already?
I mean, if you want spells to have two effects... you can already throw two spells at the same time.
How about: water walking, drain health, damage health, weakness to magic/shock/fire/ice, slowfall, burden, feather, open lock, etc.
Oh you meant neat spell effects as a result of spellmaking?
-light on target, frenzy on target
-damage health slowly, calm
-damage health, burden (won't be able to move)