Once you have gotten the magic rod, go to Tornbo Shores. Walk along th shore. On the wall to Link's left should be a crack in the wall. Blow it up with a bomb if you haven't already. Go in. A guy in there will say "I'll give you a great item for wheatever is in your B button column. Is it a deal?" say no. don't leave but get your shovel in the B button column. Talk to him again and say yes this time. After you've traded don't trade back even though he will. The Boomerang can act like a sword and kill enemies and can pick up items! Cool huh!?