Aside from cards on the Banned List, this category has no deckbuilding restrictions, so you can feel free to build around early-game combos and mass land denial and include as many Game Changers as you want
9 Elesh Norn, Grand Cenobite Elesh Norn isn't just one of the best mono-white Commanders, she's also an excellent card to put into a lot of white decks as part of the 99
Barrin, Master Wizard (Saga/Legacy/Destiny) Barrin, Master Wizard, though a very fragile 1/1, basically turned every card on your side of the board into an Unsummon
Its also a Zombie
For those who are not interested in spending $20+ on a single card, Oreskos Explorer and Knight of the White Orchid are likely to stand out compared to Smothering Tithe and Land Tax
Lets be honest, you want this card to cheat your massive threats onto the battlefield