...What would they be? Would you use Death Sentence to kill mosquitoes? Would you roast your neighbor's lawn with Firega? Would you use Quick to do your homework in half the time? Would you Mini the guy who bullied you and then stomp on them?
I personally think having a Silence spell always at the ready would be pretty sweet. Someone starts yelling at me, and ZOT!, they're a nuisance no more. So what about you?