Here are a few things you can and can not wish for

1. You may not wish for immortality
2. You may not wish for a peice of the triforce
3. You may wish for any mask but Majoras Mask or the Feirce Diety Mask
4. You cannot wish for more than 3,000 power level
5. You cannot wish for more than 10,000 rupies
6. you can wish for any sword but the master sword, the double-bladed helix sword, and the double-bladed master helix sword