Part of the external male genitalia. Also serves as the mode of urination for males who have not undergone a Urethral reroute. A wide variety of piercings on the penis are possible:
(Note that the pubic piercing is drawn with a CBR, but this is not appropriate jewelry for a surface piercing!)
Penises can also be modified through Subincision, Circumcision, tattooing, and many other ways.