On Mission 5, A.K.A. 'A new life' there is a chance for you to get a secret rating. This secret rating is called Slugger. The only way for you to get this rating is for you to kill every person in the level...using a baseball bat as your weapon. You can find the bat in the garage across the target's house. Just make sure you kill all the guards, the target, his wife, the garbage truck workers, the man jogging, and all the other people on the level. You will not get anything by completing this way, but it is fun. If anything, it will be hard.

Alright, I was very surprised that I did not see this submitted anywhere in this section, so here it is. Now those of you who do not know about this cheat, will know.

This trick can be done any game difficulty where you have a limited number of saves. It can be used on any level, and as many times as you possibly want to use it. There is no limit to the trick. Now, what the trick does exactly, is give you unlimited saves. It makes it so that whenever you save, your number never decreases. Now, the actual trick is simple. While saving press start repeatedly till it is finished. Just keep pressing start. Thats it, if you started pressing the button at the right time, then your number will have not decreased.

Hope this helps.

Pass the game then
Play any level on any difficulty
To play the level with all you're unlocked upgrades from the previous go
And you also unlock level select

Now thats cool!