For competitive players, key cards like Jack and Whos Who are staples in black decks
Pauper is loved because its comparatively budget-friendly while still being competitive and deep
This makes collecting new booster packs from winning battles even more exciting, as the next one you receive could very well be the one to enable a new evolutionary line or make your collection big enough to handle multiple decks
For 6 hard-to-cast mana in a world where people are running too many fancy lands and not enough basics, the upside of Wake of Destruction keeps shrinking
The creatures do have to be small enough of course, but many White decks are already interested in small low-to-the-ground creatures anyway
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)