Sex - The Bus Driver
A guy gets onto a bus and sees a rather good-looking nun. Having a bit of a thing for nuns, he goes over to her and starts chatting her up. She immediately flees, leaving him alone on the bus. The bus driver pulls over and says to the guy, "Listen, you'll never succeed like that. That nun rides this bus every day. She's a widow, and has taken a vow of chastity. She's married to God now."
The guy says to the bus driver, "So, what should I do?"
"Well, I don't know entirely, but I do know that every night she goes to the graveyard to mourn her late husband." At this, the guy begins to think of a plan, confiding it to the bus driver.
Later that night, he goes to the graveyard. Sure enough, there's the nun. This time, though, he's wearing a mask so she can't see his face. He walks up to her and tells her that he is God. Immediately, she gets down on the ground and says that she will do anything he commands. He grins and says that he wants to have sex with her. She thinks for a moment and says that because of her vow of chastity, she can only do anal sex - and since she was cleaning her husband's tombstone, she happened to have some Vaseline. The guy was more than happy, and they proceeded to go on for about ten minutes. Satisfied, he sits down and says "By the way, there's something you should know." Pulling off the mask, he says, "Surprise - I'm that guy from the bus!" The nun reaches under her habit and pulls off a mask. "Surprise - I'm the bus driver!"