Q: What has three nuts and comes from outer space?
A: E.T. - The Extra Testicle
Q: What do you call a hundred head of cattle masturbating?
A: Beef Stroganoff
And my personal favorite that I bring out on occasion is to mention that I'd like to get tattoos of Frankenstein and the Wolfman (one on each breast) and say that I'm going to ask if people want to see the monsters.
There is also the old standby:
Q: Why did the chicken cross the road?
A: To fuck the duck on the other side, he was a pervert.
What? Oh don't look at me like that, they're funny! *snicker*
So what are you favorite bad jokes?