Nidoking has the following attacks: Poison Horn - 90 damageYour opponent's Active Pokmon is now Poisoned.
Circle of Flame can keep hordes of Saprolings away when someone might be tempted to send the swarm at some of your Planeswalkers.Vortex Elemental and Mogg Maniac can persuade someones large threatening creature (say, Lord of Extinction) to attack someone else
Not necessarily because it's ultra-powerful, but because it can create such a big reset, forcing everyone to start rebuilding from scratch, and Wizards thinks players should have the option to opt out of that experience
Unstable Amulet I dont think you need to be an energy deck to play Unstable Amulet as long as your strategy gets lots of triggers for casting spells from outside your hand
And no, it doesnt mean that you slap someone with a fish
This monster from Raging Battle is really useful for Xyz Summoning, because she can Summon a matching-Level monster when you play her