The Love Hotel (U+1F3E9) is rather obvious, maybe the kiss mark (U+1F48B) as well, though the raunchiest ones (in actual use) are a bit more… discreet?: the aubergine (U+1F346) and splashing "sweat" (U+1F4A6).
I'm not sure what use that would be? U+<hex> is a normal way to designate codepoints, and I can't put the actual emoji in the comment as they're stripped on submission.
