normal acorn
Maybe this would break the game or let you get OP too fast with collecting more relics or gold than you're supposed to, but.
If you have the levitation relic that let's you float over pits, it sucks you can't move back to previously unexplored Dungeon after the floors fall away. I'd also love a mark that let's you do a single high jump, so you could rarely use it to gain access back to previous Dungeon segments prior to the ledges or holes in floor. (Obviously you'd have to be willing to give up much better marks for this Dungeon exploring one.)
storm tiger