Oh, so many moments to choose from....one moment that just cracks me up is at the end of movie 6, when Gokuu and Vegeta are gently floating down to Earth after the battle with Coola, happy music is playing, everyone's cheering for them, and then BAM! they both make a not-so-graceful crash landing
I also thoroughly enjoy the scene where Vegeta figures out that Gokuu is planning to appease the Elder Kai by giving him HoTT piXxX!!11 of Bulma. It's the only time we get to see him go super-deformed in the manga.
Oh, and cross-dressing Trunks from GT! He made such a radiant bride (and had a wicked six-pack, to boot

) Another GT moment I like is when Vegeta rips the steering wheel from the car of the guys who were hitting on Bra. Speaking of driving, the whole episode with Gokuu and Piccolo learning to drive was pretty damn hilarious. "Cut the steering!" *Gokuu breaks off the steering wheel*
I can't think of any specific dub quotes that I find funny that people haven't mentioned yet. I know I generally find Oolong to be funnier in the dub, though. As for lines taken out of context to sound sexual, I think my favorite is when Krillin is about to use Bulma's Patented Android Deactivator on #18, and he says something like "This device will immobilize her, but then I have to do all the rest!" Damn, Krillin, you just don't want to do ANY of the work, do you?