a huevo
It means eggs but people use it so much for balls that you better be ready for a little embarrassment if you're a girl
I said, "I want a huevo." The waiter said, "Are you sure?" I said, "Yes."
She asked, "Do you want a huevo?" I said, "Sure." The waiter looked at me like I was crazy.
He said, "I want a huevo." The waiter said, "You're brave."