I would have to say my third nipple. Everyone thinks it's exciting to have one but it's not really, it's like being a twin - you don't know what it's like not to have one.
I have a love-heart shaped nipple too but i should save that for if you ask a Q. about most favourite parts.
Ciao!
"Jonny Tightlips... you're shot! - whered' they get you?" "I ain't sayin' nutin'." "But what'll I tell the Doc?!" "Tell'um to suck a lemon."