Hearthpwn

You can look at Wild for those answers. The big 2 I can think of are Swordfish and Neptulon. Standard doesn't have the draw between Secret Passage and Cutting Class where a 12 damage weapon can effect the meta as much as it does in wild. Neptulon isn't seeing play in standard, but if something gets printed to rez or cheat it out, it'll get nerfed real quick. Cancer Priest can get Neptulon out turn 2 with coin, then 40 damage to face turn 3 with coin and the right draw.