Gift of Tusks Sometimes the best tricks are the ones that completely rewrite what a creature is, and Gift of Tusks does exactly that
Chances are most of your decks wont be five color good stuff, and if thats the case, this card can give you the breathing space you need to win games
In many ways, the Spellbook is a better recovery option than Locations because Ruby/Amethyst has not answer for it, while it can pretty reliably take out locations via Maui
Honorable Mention #1 (#13
If you're unfamiliar, here's a list of the ten two-color pairs (and their commonly referred to name) and how they tend to play in Commander (at least according to me)
These decks are specially designed to represent the best of each group, with new cards and fancy mechanics to keep you playing long into the night