Honorable Mentions It wouldnt be fair to have the conversation about countering spells without mentioning some of the most format defining cards
It uses a simplified model of the rules of Magic to perform a large number of playthroughs, each starting with a randomly shuffled deck, while recording whether were on or ahead of curve on each turn in each playthrough
Timmy cards usually have high mana costs with a huge, paradigm-shifting effect alongside big bodies and more than a few evergreen abilities like flying, trample, or lifelink
Beyond that go for faster lands Sanctum of Ugin, Ancient Tomb, Eye of Ugin, better ramp Mana Crypt, The One Ring for draw, the Eldrazi Titans (all), Conduit of Ruin, Void Winnower, Portal to Phyrexia, okay I'll stop now