Playing big spells for a lot cheaper than what you normally would
In Return to Ravnica block, a new ability was given to split cards, fuse, which allowed you to cast both halves
Sure, you can use it to trigger madness or discard flashback and so forth, but its good just to sift through your deck
It shaped the way red turned out to be in the color pie, as Richard Garfield recalled in booklet found in From the Vaults: Dragons : The biggest effect of Shivan Dragon on how the Magic game turned out may be that its the biggest reason red has flying
An Explosive Vegetation redundancy for those of you not playing Planechase, or also a voting card for those of us who are (although Im going to wait to play in-person
Coercive Portal Coercive Portal is a weird case: a card that seems designed with multiplayer in mind, but one thats great in 1v1 since you're guaranteed one free draw per turn if you want (since homage wins if it's a tie)