I can't believe I don't see my all-time favorite joke either in this thread or in the archived one Dark Jezter gave a link to! No idea where I first heard it, but it was several years back, and I don't remember it all, so I'll have to ad lib a little....
A pair of very virtuous paladins arranged a rendezvous so they could swap stories of good deeds done, foul monsters vanquished, etc. The first arrived at the meeting place, and a few minutes later the second showed up, riding on an unfamiliar horse. After a few words of greeting, the first paladin motioned towards the horse and said, "I can tell there's a story behind your new mount." The second paladin nodded and proceeded to tell the tale.
"On my way to our meeting, I was traveling through the woods and heard someone crying out for help. I raced forward and found a young maiden on horseback surrounded by a dozen goblins. I charged to her defense and slew all the goblins. The lass insisted that I take a reward of some sort, even though I told her that none was expected.
"She climbed down off the horse and peeled off all her clothes, leaving them in a pile by the horse. Then she slowly approached me. 'Take anything you desire from me,' she said in a strange, husky voice."
The first paladin looked at his comrade, then at the horse, and finally nodded.
"You chose wisely," he said. "The clothes would never have fit you."