If a Zombie card is put into your graveyard during your main phase and the stack is empty, you have a chance to cast it before any player may attempt to remove that card from your graveyard
Beyond those three, its anyones guess, but Ive been through the list of available mechanics and keywords to pick out what seems the most likely: Battlecry A Go Wide strategy is likely given the huge armies and battles in the series, and battlecry is a way to help break stalemates
Beyond boosters look like the more realistic purchase for those who are trying to collect some of the new cards but dont necessarily care about all the fancy foils, Booster Fun treatments, and so on
You could sacrifice a creature an opponent owns if you gain control over it, but this is also a relatively rare occurrence
If Wizards prices this correctly, Scene boxes could become an all-timer product to match the introduction of the Set booster or the Commander precon
See, your mom was right