Activating this trainer:
If not state otherwise below, press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.

Promo Options:
NumPad5: Unlimited Ammo

Trainer Options:
NumPad1: Unlimited Health
NumPad2: Unlimited Shields
NumPad3: Player Invisible
NumPad4: Unlimited Jumps
NumPad5: Unlimited Ammo
NumPad6: No Reload
NumPad7: Unlimited Grenades and Throwables
NumPad8: Easy Kills
NumPad9: Unlimited Jet Thrusters
Multiply: Freeze Challenge Timer

Editor Options:
Experience Points: Agility XP
Experience Points: Special XP
Experience Points: Driving XP
Experience Points: Explosive XP
Experience Points: Firearms XP
Experience Points: Strength XP

Notes:

THIS TRAINER IS FOR THE CAMPAIGN ONLY!  DO NOT TRY TO USE IN WRECKFEST, YOU ARE LIKELY TO BE BANNED!

EDITOR OPTIONS

For Experience Points, load into the game, note the values, edit the values then press TAB to lock them in.  Values of 50,000 to 100,000 may be needed to max the category.

IF YOU HAVE TRAINER HOTKEYS WITH RED (!), then go here:

C:\Users\<your user name>\AppData\Roaming\Cheat Happens\Trainer Settings

and delete the file:
65398.xml

to reset the option keys when the trainer isn't running.

Unlimited Health:
Toggle on to try and keep health at 100%.

Unlimited Shields:
Toggle on to try and keep shields at 100%.

Player Invisible:
Toggle on and most enemies cannot see you on foot.

Unlimited Jumps:
Toggle on and you can jump as many times as you like, making reaching things much easier in the game.

Unlimited Ammo:
Toggle on and most weapons have unlimited Ammo.

No Reload:
Toggle on and most weapons you can fire without stopping.

Unlimited Grenades and Throwables:
Toggle on and you can throw many items like grenades unlimited.

Easy Kills:
Toggle on and the damage in the game is ramped up tremendously.   Many things, including cars and friendlies, can be killed easily so use only where needed.

Unlimited Jet Thrusters:
Toggle on and you can engage the forward thrusters on your jetpack as many times as you like while in the air.

Freeze Challenge Timer:
In the game there are some challenges where your score is higher or you have Gold/Silver/Bronze depending on how fast you do something.  Toggle this to try and freeze the timer