I've heard the saying "a hole's a hole" a few times before, but I've seen a couple of things on this site take this saying to its logical extreme. Namely images tagged as aural_penetration, urethral, nipple_penetration, blowhole_penetration and navel_penetration (and how's this? The last one isn't even a hole! I don't even...).
I suggest that we should have all those tags imply a single one, (unusual_penetration, maybe?) and, while I don't have any particular reason to suggest that, metatags are a good way to organize and link everything together, whether it is so people can blacklist it or because they're into that kind of thing.
There are some, right?
Updated by SirAntagonist