I'm told med students and ER workers have a wacky sense of humor too. I'd bet that most folks working in life-or-death occupations blow off steam with jokes that would freak out peaceful desk jockeys. I work in IT these days, and even on the worst days(*), as one of our guys says, "Babies ain't dyin'." But at lunch some of our jokes might make the system users shiver. We have a team of people who like to help, but when the same (otherwise brilliant) fellow keeps coming back with the same problem, he can expect there to be a little behind-the-scenes merriment. But we'll cheerfully keep fixing the problem.
Prediction: Among themselves park rangers will have wry jokes about bears and over-confident hikers, ambulance drivers will have coarse phrases for frequently visited locations, and firemen will have theirs about places and stupid people tricks.
(*)E.g. When we lost an un-backed-up 3PB filesystem. We were saying to each other "Well, they needed more disk space, and now look--3PB of free space!" We got the system fixed, and only lost about 100,000 files, almost all of which were reconstruct-able--not too shabby.