There are ruins, scattered about the world, and all are sealed with unbreakable locks.
When all of these locks suddenly open, what emerges?
A cave with weapons sunken into the walls, blades sticking out of the floor and ceiling, and so on. Possibly, any weapon used in it could be torn out of the hand and sink into the stone.
Other improvisational weapons/tools:
Icicles are useful as daggers,
Bag Of Holding filled with copper pieces used by chucking the contents at foes, (by strolen)
sleeves make useful garrotes. Ya can't cut anyone's neck, but you sure can choke 'em!
Flaming Logs make great clubs, (any Barbarians out there?)
and Bee hives are very effective when thrown at a mob of enemies. :-)