Daikatana 64

At the Stage Select screen press C-Up, C-Right, C-Down, C-Left, R, L, Z, C-Up, C-Right, C-Down, C-Left to unlock all stages. A scream will confirm that you've entered the code correctly and the level select has been enabled. Use the analog stick to select stages and worlds at this screen. You can enter both this code and the Unlock Weapons code before any level.