You can unlock a Cheat called 'Giant Stetson Mode!' then enable it in the secrets menu!
PC and Remastered Location:
Go to the Undercity (The Fogometers in Shadow Man Remastered). Go to the ledge where two snipers are awaiting your disposal. Jump to the ledge on the right, climb onto the next ledge, and look for the curved U-shaped pipe. Jump to it and the "Secret Activated" message will appear.
N64 & Dreamcast Location:
Not avialible on these consoles