Broken Sword

The broken sword appears in several Zelda games.

Ocarina of Time
Also known as the "Broken Giant's Knife", the broken sword is the handle and portion of the blade remaining from the Giant's Knife. The remaining handle can still be used as a weapon, but will only inflict 1/4 the damage of the original Giant's Knife. If you return the broken sword to Biggoron, he will forge you a new one.

However, if you perform a trading sidequest, you can get a more sturdy Biggoron Sword, which will not break.

The Minish Cap
Not so much referred to as the "broken sword", you recieve the broken handle of the Picori Blade early in the game, which Melari will reforge for you later in the game.