Is it Cheating?
Whether or not using a GameShark code is considered as cheating is to some extent a matter of perspective. However, most people would consider using codes to give them unfair advantages in combat, get game items and money, or super charge Pokemon stats as cheating. Some codes are a bit more questionable as to whether or not they are actually cheating. Some Pokemon are not catchable in Pokemon Emerald due to Nintendo's policy of requiring players to play or trade with every version of the game to acquire every Pokemon. Using codes to allow Pokemon not normally accessible in Pokemon Emerald is a bit more questionable. Those codes don't make the Pokemon easier to catch, they simply make them accessible.
Are There any Risks?
Yes, using codes can cause many problems. It is even possible to inadvertently corrupt a saved game or place yourself in a situation that might not be fixable with any amount of codes. The chance of this happening increases with codes that cause things to happen that should not be possible at that point in the game. When using cheats, avoid giving yourself storyline-related items to minimize these risks.
Why Isn't a Code Working?
There are three common reasons that a code would not work. The first is that the master code was entered incorrectly or the wrong version was used. The second is that the code itself was entered incorrectly. Entering too many codes at the same time, or entering conflicting codes, will cause problems, as well.
Are Action Replay Codes Compatible With GameShark?
Action Replay codes can be entered with GameShark, but the two systems are not completely compatible. Some Action Replay codes may not work or work sporadically when using GameShark. GameShark and Action Replay codes cannot be used at the same time because they both require different master codes.
Where can I Find GameShark or Action Replay Codes?
The official GameShark, Action Replay and GameFAQs websites all contain codes that can be used for Pokemon Emerald. Links for these websites can be found in the Resources section below. The codes on GameFAQs are more oriented towards accessing unavailable content. The codes on the GameShark and Action Replay websites are more oriented towards cheating.