Resident Evil 4 Cheats

Whenever you have the chance to dodge (A and B, or L and R), if you are in the middle of a reload (Or just started one), and you perform the dodge, after you dodge your weapon you will have a full clip of ammo, as if you fully reloaded it. Useful for fighting bosses where you don't have a lot of time, or when you must reload an item that would normally take awhile (Such as the Broken Butterfly).

When you get to the second wave of enemies when Mike is helping you, destroy the guns with the Infinite Rocket Launcher BEFORE you enter that area. Once you go past the shutters, the Ganados will rush to their posts, but only to die immediately. It will also work with the regular Rocket Launcher, but that only has one shot, so... yeah.

In the castle, there is a glitch where you can make the Gatling Gun appear without allowing the red monk to operate it.

First, progress normally and let the red monk escape. Once you return to the turret room, he will be operating the gatling gun. Immediate leave the room and return to the main hall with the merchant and save.

Load the game and re-enter the turret room. You need to chase the red monk again until he returns to the turret room. When you return to the turret room, the turret will be raised, but the red monk will be standing outside of the turret ring! Without the turret on his side, finish him with ease!

To do this, you need at least one normal weapon, and the Infinite Rocket Launcer.

At the begining of each chapter hit an enemy with any weapon once (any weapon other than the IRL) You can then fire away at anything with the Rocket Lancher, no matter if you hit or miss an enemy, and you will get 100% hit rate at the end of the chapter.
This happens because the game does not register the Rocket Launcher hits like the other weapons hits.