You might need to sift through to find what youre looking for, but for those willing to spend time instead of money, buying cheap Pokmon cards can be a very cost-effective way of building up your library
4 Scalelord Reckoner ( F, LC, PF ) - Similar to Thunderbreak Regent, but with a more powerful effect in white, downright destroying permanents
For four mana, you get a 4/4 that lets you sacrifice a creature on attack to add Red mana equal to its power
The ten listed here are just the tip of the iceberg
Wrenn and Realmbreaker Wrenn and Realmbreakers emblem cracks games wide open, especially in grindy matches
Just for the sake of being complete here, the Tropical Island card (also found in that video above) rounds out most top 10 lists but is not considered part of the Power 9