The Mewtwo EX card quickly came to dominate the TCG's meta when it released as part of the Next Destinies expansion, and with good reason
I can see that strategy ending a game in your favor
Thoughtseize (and Inquisition of Kozilek) Something that I see in a lot of Cubes is players including discard spells that are specific to their environment and eschewing the more generic Thoughtseize
Near-Death Experience Balanced right on the edge of losing, Near-Death Experience asks you to start your upkeep at exactly 1 life
This variant of the Articuno ex strategy is more reliant on Misty than the other variants, as players are expected to use the Greninja line as an early attacker while Misty gets energy attached to Articuno ex
1 Arcum's Astrolabe It's hard to talk about the most powerful snow cards without talking about the only snow card that's not just banned, but banned in multiple formats (Modern, Legacy, and Pauper)