The standard set contains a holographic Dark Dragonite 5 and a non-holographic variant (22)
Given how easy it is to draw extra cards with Loot, you ideally also want a lot of mana to work with
Furthermore, the fruit fly is small but large enough to be easily observed under a microscope, can reproduced in the millions and quickly (a new generation every 10 to 14 day at 25C or 5-6 weeks at 18C), and has 75% of the same genes that cause human diseases
Id really love to be playing Blinky the Eldrazi, aka Eldrazi Displacer, as often as possible
Other good payoffs are spells with X in their mana cost like Crackle with Power, Mass Manipulation, and Animist's Awakening that benefit from pumping tons of mana into them
Are there any must-have cards that Ive skipped