The cheats of Roller Coaster Tycoon 3 are the only ones that really work in the entire series. The first and second game didn’t have any cheats at all, but still they were easy to play and beat the scenarios. The third game was the first game to have the inclusion of cheats because some scenarios were a little bit difficult to complete without the help of some codes.
One cool thing about this game, is that every cheat that is known actually works, and that's something interesting because like many other games with Roller Coaster Tycoon 3 you will know that all the known cheats will work without any problem.
To activate cheats you need to write down the command in any guest name, let’s say if a guest is named <Kathy D>, I erase her name and I write down one of the codes <code>. When you write the code down in the guest name you will see the cheat activated, but if you want to activate the same code multiple times you need to change the capitalization of the code, i.e. code 1: <John D. Rockefeller>, code two: <John D Rockefeller>, the modification in the capitalization will work and you can input a code multiple times, except the terrain codes.
Make Me Sick: all of the guests become sick. This is a funny command but is not good if you are trying to achieve the goals of an scenario.
Mouse: All guest look at the ground.
Atari: All guests start to laugh hysterically. There is no real use for this cheat except if you want to laugh too.
Frontier: The rides never break down, this is probably the second best cheat in the entire game as some scenarios have the requirement to maintain a perfect score without any breakdowns.
Atomic Big Explosion: Never use this one except if you like violence, all the coasters in your park will crash.
John D Rockefeller: Gives to player US$10,000 (it can be used different times, changing the capitalization)
Melanie Warn: The happiness of guest its increased, good for missions that require certain amount of happiness with the guest.
Jonny Watts: You can see the theme park in first person perspective trough one of the guest point of view.
Sam Denney: The guests rides the roller coasters in your park.
John Wardley: In my opinion is the third best cheat of the entire game, as some scenarios require you building certain roller coaster with restriction heights but with certain requirements as a high Nausea Factor (is just an example), this is the best cheat to because it let you make a simple high roller coaster and avoid the restrictions. Removes height restrictions when building coasters
Truly the cheats make the experience really comfortable, but most of the missions are really easy to win and there is no need at all to use the cheats. Personally I only used once, but because I was really desperate to win the third scenario, but the rest of them were really easy. Also you need to know that the cheats also work with the expansion.