I would take the door door fruit, because like almost every paramecia in the entire series, it is mind-bogglingly powerful with the right use. on the assumption that this is real life, Bam! you fall through the trapdoor into a volcano. if this is in the one piece world, Bam! you fall into a sea king.
Plus, hypothetically infinite piercing power by just turning whatever the f*** you are stabbing into a door. And i can teleport. And i get a free pocket dimension. And plenty of other just plain unfair powers.
Or failing that, probably kizaru's, because Pew Pew Pew! death rays!