The insistence of my dwarves in picking up bins full of multiple sets of steel armor, dragging them all the way to the surface, and onto the battlefield so they can put a helm that one of my military dwarves randomly dropped back in the bin. It isn't just after battles of course, dwarves going off training like to leave armor and weapons scattered about, so of course what must be done is to drag up the bins from my guarded armory to put it all back.
Once they do this, they seem to realize the futility of the whole operation and just leave the bin there, so that days later some other dwarf can remember that there's about 50,000 dwarfbucks of valuable armor sitting on the surface and maybe they ought to put it back in the stockpile.
They monkey around with weapon bins in the same way. Every time I want to make a weapon trap, I have to wait and pray that they stop dragging around the bins long enough for me to designate some deadly implements for my traps. Half the time all I have available is a few large daggers, when I know I've got large serrated blades and giant axe blades floating around somewhere.
I suppose I could remedy this somewhat by splitting up my weapon and armor stockpiles more. If I had one for steel battle axes, one for iron, etc, then they'd logically be dragging around less full bins, at least. On the other hand every time they do that, we'd lose access to all our spare steel battle axes all at once, and I'd have dwarves going on-duty being unarmed and possibly not finding a weapon to use before going into combat. I've set all my axe dwarves to chop wood, but they still like to drop their axes when they go on/off duty, and all my other military dwarves are out of luck.
I'm tempted to go without bins altogether, but I don't think I have the space. I've already tried adding wheelbarrows in the hopes that this way only a single dwarf per stack would be running around swiftly with the wheelbarrow, but this only works for bin retrieval. My other haulers are still dragging the bins by hand up six flights of stairs and then dropping them out in the barracks or out in the field, only the trip back is quickened and now I only have as many dwarves taking them back into the stockpile as I assign wheelbarrows to that stockpile.