I say Saints Row 2 ... All because I watched my step daughter play that game with cheats and had a lot more fun then when she didn't use cheats

My 2nd choice would be Cheats in the Original Goldeneye, but you would have to unlock them first :) by doing all those timed missions ...

God, I remember refusing to play Grand Theft Auto 3 without the cheats on back when that style of game was alien and frightening.

If you really want to play a game that is the lizard to cheating's Geico, I'd grab The Orange Box for the 360. You can cheatslap Half-Life 2 until your'e sufficiently satisfied, then turn to Portal and run its amazing physics through the wringer. Boot up the "place portals anywhere" code and understand why PC gamers have more fun.

An interesting example of creative cheatcodes can be found in the transition between Doom and Heretic; two 2.5D FPSes published/developed by id (Raven co-developed Heretic) for the PC.  For Doom, IDDQD was godmode, IDKFA was all keys, weapons and full ammo, I believe.  

Heretic had cheats as well that did similar things, but if you tried to input the Doom cheatcodes, you got some funny results.  Typing IDKFA resulted in your inventory being emptied, leaving you with your melee staff and the game said "Cheater - you don't deserve weapons!".  Typing in IDDQD insta-gibbed your character in a gruesome manner, and the game said "Trying to cheat, eh? Now you die!".  Fun stuff.

Typing "cockadoodledoo" transformed you into a chicken.  Also amusing.

@Alan I totally agree with Grand Theft Auto 3, or any Grand Theft Auto game that was on the PS2/Xbox. Those games just didn't make sense without cheating. It's funny because I put over 100 hours into Grand Theft Auto IV and haven't used a single cheat.

@Toby The timed mission are one way in Goldeneye or you can enter a bunch of cheats on the Mission Select Sceen. Saw them in an EGM like two or three years after GoldenEye came out.

If I were to cheat in a game today it'd be... Silent Hill: Shattered Memories, but that's only if you consider using a strategy guide to beat the game, which is what I used.

I don't like the Grand Theft Auto series at all, but I'm going to echo the earlier sentiments: Those games are a blast when you're cheating. It's the only way I ever get anything out of 'em.

To start off with, I will never join the group that is "All cheaters are evil!" So long as it's me against the computer, which tends to cheat in of itself, All's fair in love an war as far as I'm concerned. That said, it's not the game that's important, it's the cheats. I myself avoid ones which make the game dull. Hit the opponent anywhere on a fighting game? Boring. Wipe out ta screen of enemy forces in a RTS? Snorefest. Infinite HP in an RPG? Uness you're talking going against enemies which will wipe you out regardless of stats, it's no fun. The cheats I use don't detract from the goal, it just makes absolute failure non-existant. Some guidelines I like to reccomend:

1. Consider your goal. Do you want to steamroll a game you've already beaten, or do you just want to get past a particularly frustrating part? Do you want the odds in your favor, or just to see some weird stuff? And how far do you want to go on the edge you've given yourself? Find out what you want out of your gameplay and go for it.

2. Go sparingly. A number of games have a mess of cheats for them, most of which are redundant or unnessesary. Once again, look at what you want out of the game and find the codes to mesh with that. Out of 20+ codes, you might find you only need 2.

3. Keep separate saves. This is especially true if you're using "unofficial" cheats, like a cheat engine for a console or a trainer for PC. Saves can get corrupted and if a game has an anti-cheat checker in the save system (bunch of jerks that do that!) it can really screw up your progress. Backup your non-cheat saves on a different storage location if you can and save frequently on your designated cheat save location. Remember the old mantra, "save early, save often." More so that you can spot problems quickly instead of after 20+ hours devoted to the game.

4. Keep it offline. Me vs. computer, all bets are off. Me vs. another player? Follow the rules. You do online play to test your skills against other people, not to brag that you are invulnerable as you kick them to the curb. Cheating online will earn you no friends and make you a lot of enemies. Co-op against the computer, if all players agree, I treat the same as solo play though, but only if everyone agrees. Achievements are an interesting grey area. As far as I'm concerned, if you care what others think, then use a non-cheating save as your storage record. If not, then have fun.

It's interesting to note that for the PC version of Fallout 3, you can enter "debug" cheats that can refill your ammo, health, armor, pretty much anything to your personal benefit, and I noticed that unlike say... GTA4, where after entering certain cheats your achievements are disabled, you can cheat your way through Fallout 3 and still earn achievements towards your gamerscore.

That's pretty cheap.