I can definitely cum from having my nipples played with. I haven't been able to achieve orgasm myself, but with a partner it's actually quite easy. Sometimes it's from soft play, him lightly licking or sucking my nipples while gently squeezing my breasts. Other times it's from harder play, if I'm already worked up to the point where my clit is throbbing it doesn't take much more than a good hard pinch or pull on my nipples to have me gushing. Both are fantastic.
It only happened to me once, but it was fantastic. Now, when I am about to have a clitoral orgasm, I like having my nipples pinched or bitten to intensify my pleasure.