While very niche, I found something mildly not trivial!
After a little !!SCIENCE!!, I have discovered a cool bug with artifacts. If you forbid the main ingredient of the artifact while your moody dwarf is working on it, the artifact will be made from iron.
If you forbid all ingredients, then the moody dwarf will "work" for the entirety of their mood timer and then go insane.
There are practical applications for this, like if your moody weaponsmith who likes warhammers goes off and grabs some candy, you can forbid the candy to not only save the wafer but also to produce a not useless artifact. It can also be used on moody children to create useless iron artifacts rather than useless bone or wood artifacts, which can help your wealth or at least make the artifact feel a little less useless. Note that they will still train the original skill and not metalcrafting, unfortunately.
This needs more !!SCIENCE!! of course, since I have a sample size of one, which was a moody child destined to make a wooden cup. I'm still curious about several things, like how a clothesmaker's mood might be influenced by this. If anybody gets a moody clothesmaker, I'd be very interested to hear what happens if you forbid all the cloth they gather.