A single 2 to 3 hour session can really nail down the specifics of a matchup
Tinker is absurdly powerful, but even it has nothing on the number one card on this list
Creature - Kobold Color tag templates(None) Mishra, Lost to Phyrexia Whenever Mishra enters or attacks, choose three Target opponent discards two cards
Battle for Baldurs Gate: Blue Blue has a bunch of cards in this set that care about your own board investments, which sees a marked shift from what blue is usually doing messing with other peoples stuff
Ultima The five-mana board sweeper, Ultima, is seeing play primarily in Domain Overlords and Azorius Control
This idea was first explored in Final Fantasy 9, of course, but something has to be said for how acutely you feel the difference in scale here