I wish I had a Predator Ooze in my starting collection (and you can, with the Foundations Starter Collection!)
Now you have a 4/4 on turn 3 that can then grow to a 8/8 on turn 4
You can also use him to ramp into bigger characters early, by chaining his ability to get out something like Doc - Leader of the Seven Dwarfs on turn 2 and then using both their abilities on turn 3 to play a 5-drop
Miirym, Sentinel Wyrm It's hard to top Miirym, Sentinel Wyrm a.k.a the Dragon queen of value
Serum Visions, Opt, Sleight of Hand and Cling to Dust have all made the deck at some point, but none of the Modern cantrips are quite strong enough to match the consistency of something like Ponder
We will be excluding enchanted rare cards in this list and only talking about the most expensive legendary cards