Pro Tour Gatecrash Quarterfinalist Melissa DeTora: I think it's Last Breath. Everything you want to kill is two power or less.
No. 12 Ranked Player Owen Turtenwald: Probably Supreme Verdict. That counts as removal!
Grand Prix Atlantic City 2013 Champion Jon Stern: Hero's Downfall. You have to be able to kill planeswalkers and Nightveil Specter. It does a lot of work in a lot of matchups.
Grand Prix Indianapolis 2012 Finalist Chris Fennell: Ironically, Last Breath. There's no other card that kills everything you want to kill early. The only card being played that Last Breath doesn't kill early is Fleecemane Lion, and that creature's able to be targeted by every other card.