Xanathar's Guide to Everything includes the spell shadow blade, which seems intended to be used only by the caster. It creates an actual weapon (XGtE, p. 164):
You weave together threads of shadow to create a sword of solidified gloom in your hand.
However, the spell also says:
If you drop the weapon or throw it, it dissipates at the end of the turn.
Instead of dropping or throwing the sword, what happens if the caster hands it to an ally? Can that ally attack with the sword on subsequent turns (in particular, without either party using Ready to act on the same turn)? Would the sword dissipate if an ally was the one who dropped or threw it?