In Greed Mode, if a Lil' Battery appears in the Shop and a 2 of Diamonds is acquired, infinite money can be gained by duplicating the Two of Diamonds.
With a ? Card and Schoolbag, single use items can be used an unlimited number of times by duplicating the card.
Book of Virtues: Spawns two white six-sided die wisps, on the middle ring, at the same time. An extra wisp spawns if no pickups are duplicated.
D1 is the only die item that doesn't re-roll anything.
As such, its description, in certain cases, can be ironic, as the outcome is entirely predictable if there's only one pickup. This makes sense because the die only has one pip on each of its 6 sides.
As an exception, Spindown Dice, although it technically does re-roll items, has a controlled and consistent result.
D1 is the only standard die item that doesn't have the respective number of sides as outcomes, but rather, just a D6 with all sides having singular pips. Rather, an actual D1 would be more accurately pictured as a Mobius strip or a sphere.