Jayne: (calls out from across the room) "Can I start gettin' sexed already?"
Mal: "Well, that's one kind of horrific."
And my other most favorite, from the scene with Mal and the rapier fight:
Harrow: "You didn't have to wound the man."
Mal: "Yeah, I know, it was just funny."
Seems that Captain Tight Pants finds wounding people just as cheerful as I do. Especially after a rough day.