The prostate gland, said to be the male equivalent of a woman's g-spot. Capable of producing great physical pleasure with massage or pressure; not too surprising since the prostate gland produces about two-thirds of the "juice" in semen.
It is possible (perhaps more often practiced in parts of India) for the prostate gland to be "milked" resulting in ejaculation without orgasm.
"So the doctor gave me this digi-rectal exam and when his finger was all the way in, it started to feel really good. Does this make me gay?"
"No, man, it means he hit your male g-spot, the prostate. Every guy's got one."