Akroma's Memorial is a classic that gives our stuff haste for swinging now, great to trigger a Templar Knight tapping that needs them to attack as well as flying the best evasion, vigilance if they weren't a Templar, first strike to abuse that high power low toughness and then two protections to swing through many a defense
While a 3/2 for four mana isnt great, the ability to counter a wide range of effects (spells, activated abilities and triggered abilities) or destroy a creature or planeswalker when Ertai enters makes this card an amazing Swiss Army knife that can answer a number of kill-on-sight threats, often in a surprising way, as the fact that this card counters triggered abilities can really stymy a foes game plan in unexpected ways
Honorable Mention - Impulse, Common Let's begin with a card that's no stranger to anyone and came closest to cracking that Top Ten list
He has double strike, it creates a relatively powerful token, and it gains counters whenever any other creature with greater power dies, including tokens
That was very strong