In the Arena announcement, Wizards describes Specialize as a brand new mechanic, so it seems highly unlikely that they only got one use out of it
Dragonhawk, Fate's Tempest Dragonhawk, Fate's Tempest needs to be in a creature-centric deck to do real work, but it does so much if you have enough 4-power creatures (which is a lovely call back to the ferocious mechanic from this creatures plane of origin)
Custom playmat A good Magic: The Gathering playmat is the kind of thing that players will take with them everywhere
A Traditional Foil card of any rarity replaces a Common in 33% of boosters
After spending four turns dashing out and raiding our opponents life totals, you could drop Ankle Shanker and swing out with your first-striking, deathtouch board to guarantee your opponents blockers would crumble beneath your advancing horde
Rakdos forces players to sacrifice their own lands, too