Another card that I'm partial to using for wiping boards is
Arcbond.
It's somewhat situational and the damage it does is dealt to players too, so it might not fulfil your criteria, but when it works out, it's wonderful.
It's kind of like
Massacre Girl in that if you are clever and circumstance allows, you can use it to your advantage and only wipe certain creatures and leave yourself with an advantage.
3 mana instant speed is pretty good too.