If they're pulled off well.
Otherwise they just seem childish. And this seems to be the majority of them.
Like "your mom" jokes (though recently I pulled off an exceptionally great your mom joke that was more of an insult and made someone cry).
EDIT:
actually, the best dick joke I ever heard was a really long and involving one. There was a kid who was sitting in a rotunda at the college im going to, and there was a relatively attractive, albeit easedropping, girl there. So he started talking to me (I was sitting in it just relaxing) and starting telling this really vague story that made you think he could be making a dick joke innuendo but also that he was just talking straight and serious. and he made it seem like he had what he was talking about on his person (in this case his laptop whch he had open) and wanted to show it.
Well in the end the girl got too curious for her own good and asked can I see it (what he was alluding to). To which the guy smiled, stood, and dropped his pants before saying its free to look, but i gotta charge to touch.
naturally this was hysterical in its set up and while he got a mark and was ordered to pay an indecent exposure fine, make an apology to the girl (who decided to not file for sexual harassment and really saved the kid from a lot of bad things), and was told he wouldnt be able to attend classes for a week (and the leading school officer said that he should use this week to grow up and not be so immature) it still wound up being a great joke and something of a memorable incident.