Risa

Riker has a resting 'I-want-to-fuck-the-shit-out-you' face, it doesn't matter who or what is he looking at. Chairs included.
And the expression only intensified when he smiles (or looks serious, or looks angry, or eats Klingon food, ... you get the idea).

Data on the other hand is very well programmed in all manner of lewdety.

And Janeway had lizard sex with a lizard. And used holodeck exactly as everyone else on the ship - for kinky romance.

Vulcans get rapey every 7 years.

Klingons have to be bitten into sexy times.

Qs had full on intercourse in front of the camera.

T'Ana is sexy in heat.

And space-life-energy thing impregnated Troi as we watched.

~~Bortus laid a fertilised~~ whoops, wrong trek.

But other than the mentioned cases, ... only many many more are not listed here.

The prime directive pretty much has a loophole clause that it doesn't apply in situations where it could become classified as a "space-genitalia-blocker".