I got used to it, and when it became apparent that I wouldn't let it get to me, it basically stopped. What fun is it to rag on someone if the ragging doesn't bother him? Now there's occasional good-natured joking from my friends, but nothing mean or spiteful. They acknowledge the fact I have a big cock and it doesn't bother them.
There are certain situations where it is very irritating. Once at a party a girl I didn't know walked to where I was standing talking to my friends and she started up: "Is it true what they say? Are you hung like a horse?" I tried making it plain that I didn't want to follow that train of conversation, and I tried changing the topic. She persisted. At one point she said, "Well, I heard your dick is just huge." I admit it: I was a bad Whopper. My reply was, "Really? I heard the same thing about your vagina." Yeah, it was impolite of me, but how polite was it of her to continue badgering me about my cock size? Sometimes you develop a defense mechanism in response to constant teasing.