Legend Of Zelda: Links Awakening

SEASHELL MANSION TRIX :)
Go to the Seashell Mansion when you have exactly 5 or 10 shells. You'll get an extra one! And when you have 20 shells (exactly 20), you'll get a level 2 sword that shoots when Link has full health!

STEALING:
I don't really recommend this cheat, but if you're desperate enough, I guess it's all right. Take an item off the counter and go to the top of the shop keeper.
When he looks up at you, bolt out the door. Unfortunately, your name from then on is thief and if you go back into that shop again, you'll be killed. Sorry.

CHEAPER STUFF:
Select any item at a shop. Link's money is being taken, push A+B+START+SELECT and save and quit the game. Restart it with the item and most of your money you used to buy the item.

MARATHON MAN LINK:
This really isn't a helpful cheat, just something for fun.  Get the Pegasus boots and the shovel. Put the shovel on your A or B button. Put the boots on and charge up to run. 
Just before he starts running, use the shovel. Link will run in place until you push a direction button. It's actually real cute.

More music
Enter your name as ZELDA

Skip Boring Stuff
Since you probably know what a guardian acorn or piece of power does, you can press START as you hold up the item and you will not get a message about it.

Use Missles
Equip bombs on B and arrows on A. Then press both buttons to fire a bomb on the arrow (missle).