If you go and exort any store clerk ( cardealer ships, dojos, etc) and get the three !, if the option to plant evidence comes up after you get the money (note: this will give you bad cop points) plant some and then knock the guy out, then go up to his body and the option to interrigate him will come up. Again get the three ! Indicated and then either arrest,kill, or knock him out. This doesnt really do much but it was something I found out on accident. (During the interrigation, you will notice that only Marcus is the one talking and that the white line will move faster than usual after getting one of the !)

To blow your own limbs off do this

Shoot a car until it's on fire

Stand next to it or jump out of it until it explodes

You should have lost something

Note:YOU WILL DIE!!!!! ='(

You can blow people's heads off with these guns:

.50 auto(pistol)
RPG(rocket launcher)
Grenades
Land Mines

You can also blow people's arms and legs off with these guns

If you don't want to go and buy all the music in the game press start and flick over till you see the map. Hold down L&R and press the buttons X,B,X,B to get all the music. (This cheat works even though it isn't six button combinations long)