The Thing Cheats

Dont use blood tests on team members-use the test kits to prove that you are not the thing to keep them loyal.

you can try to fight the boss if u want but after you have lost and u start out from your last save piont, from there go straight to the gun turret u used to blow up the road block, in tht same room there should be an elevator go in and u will advance to the next level, it worked for me.

Highlight a flare and start it but don't throw
it down.  When it is Low press Left or Right and highlight
another object then highlight the flare again and it will restart
without using another flare

When someone's trust is in the orange and they will not do anything for you, enter first person mode and aim the gun at their head for three seconds. They will now do things for you without good trust.
Game Shark Codes
Master Code (Must Be On) 0E3C7DF2 1853E59EEE8C6406 BCBCD3EA
Infinite Health DEBD6E92 F8AADD4BDEBD6E9A 6AAA9B1F
Infinite Ammo DE4E515A E0AC9BB5

To enable Flare highlight it but do not throw it down.
Press Left or Right when it is low and highlight another object then highlight Flare again and it will have restarted and you will not lose another one.
Blood Test Kits -
To gain the the trust of your team save Blood Test Kits to show them your are not infected.
You cannot use them on a team member because they get infected randomly and usually break out within a minute of infection.

during game play pause the game and press L2,L2,R2,R2,SQUARE,TRIANGLE,SQUARE,TRIANGLE and you will have unlimited bullets. have fun.

Go into to his garage. Fix the electrical panel that operates the hoist. Step back towards the middle of the big door. There is an opening between two of the crates. Using your grenade launcher in first person targeting, send in a grenade. If the Thing turns its head toward you, then you have him targeted. Continue sending in grenades until he begins to burn. You can send in a few more if desired for extra fun. Run into the Thing's room and on the far wall from the big door is a switch. Throw the switch and watch as the Thing dies. You will probably take one hit from him.