In the first mission, when you man the machine gun to defend the base you will hear someone screaming "They're coming out of the walls! They're coming out of the goddamn walls!" This is a reference to the movie Aliens.

In the Brotherhood house, you will be trapped in a large room with zombies. Take out the zombies with your pistol and baseball bat, but save all the shotgun shells that you can. When you defeat them all, the Deer Haunter crashes through the wall. The key to defeating it is to walk in circles around the beast in the middle of the room, continually shooting it in the torso with your shotgun while taking minimal damage. When it is defeated, the door to the next room will open.

Beating the boss in Mansion of Madness involves simply side-stepping in one direction while aiming up and turning. The closer Cortez is to the fountain, the greater the chance it is to avoid being swiped. When the boss is about to die, step back and fire the last shots to avoid the final death blow.

Beating the boss in What Lies Beneath involves simply using the Ghost Gun and knowing where to stand. Locate a rock that shields Cortez's legs while allowing him to fire back unimpeded. The fire attack from the boss has to drop to the floor before moving forward; this simple rock protects the player from most of the fire breath damage. A melee attack will destroy the bats and allow the Ghost Gun to damage the tank.

Head for any ramp and stay out of the tank's sight. Use the telekinetic glove to grab the respawning ammunition to pounce the tank with rockets. Cortez wins, the tank does not.

If one character under control moves too far ahead of the other one, the one who was left behind will "teleport" a few feet ahead of the first character, often resulting in strange camera angles.

The optional task of freeing Captain Ash's ass-istant is easier than you think. Head into the prison cell on the other side and make a line of vertical holes on the metal drum from top to bottom. This creates the largest pool of petrol possible. Ignite the mess by shooting the lantern hanging from the ceiling and the ensuing explosion will give you a eyeful of T&A.

In the factory where the TimeSplitters are being incubated, the giant energy sphere powering their growth can be taken out on the top level by flicking both the switches on either side of the ball. This will lower its defense. Then, take the lift down to the floor below and throw a plasma grenade (found next to the lift) at it, causing it to explode.