You can unlock a Cheat called 'Shotgun Head Mode' then enable it in the secrets menu!
Shoot heads instead of bullets from your shottys! (Shell casings are heads)
PC and Remastered Location:
Go to the maximum security cell in the Gardelle County Jail and find the hole to drop down. Open the security gates. The cell is the one farthest to the left.
Go to Temple Of Prophecy (Marcher) and enter the "Flambeau maze". Find your way to the center of the room on the ground level and the "Secret Activated" message will appear.
Not in the N64 version.