Halo Campaign Points Trainer
Just a simple trainer that allows you to alter your points in campaign.
These points can stick and apply to the leaderboards, as seen here:
This is literally my first cheat I've ever created so hopefully everything works for you guys (also sorry for it being like the default cheat engine trainer), gave it to a friend and it worked for him.
Also note, there is a time multiplier if you played long enough. For me it was 3x, so put 1/3 of the score you want. Obviously, if you go too high it'll bug out and set the score back to zero. I haven't tried going any higher than what you see in the screenshot above.
Use the num pad to control it.
HOW TO MAKE THE POINTS STICK
1. Set the launch options of your game to "-eac-nop-loaded" in steam
2. Launch the game in non-EAC mode
3.Start any level you like.
4.Get the ammount of points you want and complete the level like normal.
If your points arent too high it'll stick.
-EDIT-
Turns out it works for halo 3 aswell.