Now I realize some of these hints will seem rather obvious to some people, but I'm trying to help as many people as I can with this. Also, most of these aren't really cheats, but spoilers, or ways of using the way neopets code is written to your advantage.
Arranged by name of the game, alphabetically.

200M Peanut Dash

Cheat: Hints: Jump Bonuses:

Advert Attack

Hints:

Carnival of Terror

Hints:

Chia Bomber

Cheat: Hints:

Cliffhanger

Solved Answers: There were too many answers to put here so they are on a different page.

Deckswabber

Hints:

Grarrl Keno

If you play this game you will lose money in the long run.
Numbers played / Payoff %:

Going to McDonalds

Level Codes and Solutions