Tommaso  Masaccio  (Active ~1401-1428)
Shows Adam's foreskin as short or partly retracted.

Capella Brancacci, Chiesa del Carmine, Florence

Leonardo da Vinci's "Vitruvian man" is much copied - though
his intact penis is seldom shown clearly. 

Again, in a few simple strokes, Leonardo indicates the corona,
the acroposthion - and the assymetrical testicles

A nude man standing facing the spectator
Leonardo da Vinci
Property of Queen Elizabeth II

One of the best known nude male images in the world. Michaelangelo's Adam is portrayed with a baby's penis - presumably to indicate his innocence. As such, this is quite accurate - a baby's foreskin may extend far beyond the end of his glans. (The closeup was taken after the recent restoration.)

One of the enigmatic male nudes (ignudi) on the Sistine Chapel ceiling. He is portrayed with a small adult penis.

David's penis is relatively small, probably to avoid attracting attention, and following classical ideals. He is intact because: Michaelangelo preferred it his model was (of course) intact Michaelangelo had regard to the midrash (Men 43 6) that David "looked on himself in the bath and was distressed he had no evidence of a covenant fulfilled" and had himself (re-circumcised) (Encyclopedia Judaica) the ancient Israelite circumcision was minimal, and/or it isn't of the Biblical David at all.
Some art historians believe that David was actually the name of the model who posed for the statue, and that Michelangelo claimed the Biblical reference to make it acceptable to the Christian world.

Hercules by Vincenzo de' Rossi
Palazzo Vecchio, Florence

Jacopo Pontormo, Vertumnus and Pomona
Fresco in the Villa Medici, Poggio a Caiano
Florence 1519 - 21

Allegory of  the Victory  of Honesty over Deceit
by Vincenzo Danti (1530-76)Boboli Gardens, Florence

Polyphemus and Acis
The cyclops' penis is boyish after the classical manner, with a long foreskin...

 ... and a detailed acroposthion.Polyphemus and Galatea (c.1597)
Annibale Carracci (1560-1609)