Beyond the most obvious useif youre using attacks that are boosted by the number of cards on the opponents benchif someone is leaving space for their vital Ralts to support their Mewtwo, or a Charmander that stubbornly wont come out to build their Charizard, filling that slot with whichever card they sacrificed up front would be extremely funny.
This is called the "black core" layer
Marvel Cosmic Invasion : Rocket Racoon's Cosmic Grenade ability has him throw a bomb that explodes with a random effect- it may simply deal damage, cause a glue bomb that slows enemies, inflict Cosmic damage over time, or there's a very very low chance of getting a Nuclear Grenade that causes massive damage to all enemies on screen
In his turn, the opponent casts Worst Fears that successfully resolves
Lets get on to that Top 10 list then, shall we
Because of this, its the more complicated of the two