[quote=@BCTheEntity]
[@RyoRyoRyoken] Well, the [url=http://onepiece.wikia.com/wiki/Horu_Horu_no_Mi]Horu-Horu no Mi[/url] does do things other than swapping people's genders. But I mean, maybe it's some form of Magic-Magic Fruit, which exhibits its full potential when the user comes up with rituals to perform? For instance, swapping genders, requiring large quantities of underwear. Oooooor nuking an island, requiring enough bombs to blow up an entire island.
[/quote]

We can all agree that the most memorable effect may have been the gender-swapping, though.
On the topic of a Magic-Magic Fruit, I'd almost be inclined to have something like that be a power of prestidigitation.

Or a "Mythical Zoan" that allows you to turn into a "Magical Girl", haha