[Wuerstchen]

Boy meets girl is one where a trans girl is shown. I dont think there is a cis girl. I mention that because although still a girl you clearly see a penis. Its a really good movie too, well worth watching IMO.
I also think that regulations are quite strict on showing a erect penis as opposed to full nudity girl. So if you do see a naked guy it would probably be a locker room scene or running down the street naked scene etc?

Trans females are female.

There is an erect penis in Pasolini's Decameron.