On the first lvl as soon as you start use the Q-claw to go up the building once up there go inside unequip your gun and chop the guards head once you have don that use the other gadgetto open the door then keep going north and you find another door once there use the card the guard gave you and you found a rocket launcher!
If you want to to use the weapons specials,just press the select button wile you have selected a weapon.like you will be able to control the MAL 22 rockets,or silence the P2K.(note:does not work on every weapon in the game)
On the level ' Night Of The Jackel' at the end when you are fighting the helicopter, keep shooting the rear propellar it sould start to lose control and start spinning. It wont shoot or dodge so you can kill it easily. This also works on the Xbox and Gamecube.
This is a code to trap your opponent in multiplayer. Go to Wine Cellar. There is a platform in the level that is activated by turning a wheel. There is also a space under it where some weapons are. If your opponent is in the space under the platform, it is possible to trap himher under the platform!!! Just lower the platform while your opponent is under there and heshe will be trapped there until time is up, unless your opponent dies!!!