I've run into more than a few men who had pet names for their penises. Women and their vaginas, not so much, aside from the usual business of preferring to call it a pussy or hooha or whatever euphemistic thing seems less clinical.
But if you are the possessor of a vagina, and wish to give it a more interesting, fun name, here are twenty nicks to avoid, unless you're way more interested in hilarity than sexytime:
ObDisclaimer: A bigger problem, certainly, is that there is a shortage of genuinely good names for a vagina. The word vagina itself is derived from Latin for "sword sheath". Yoni? Sure, let's go with that.