In the mythical story of Tarpeia, she is pelted to death with the shields of sabine soldiers (she betrayed the romans to them in exchange for 'what they wore on their arms', meaning their golden armbands). But that story probably isn't based on any actual event.

The spartans had a tradition that they should never abandon their shields in battle, supposedly because that was what you did when running away from the enemy in ancient greece. I've seen some speculation that rather than simply dropping the shield to save weight, warriors sometimes threw their shields at the enemy as they turned to run, hoping to disrupt their formation and delay the pursuit. As far as I know that isn't based on any historical account though.