TheNiceOne
Emperor
A pretty ambitious subject title, and it says more about what I want this post to be after input, than what it already is. But I think its time we have a complete list of AI cheats, so I start one and will edit it as necessary. I would really like some input from someone who knows the inside of the game (someone from Firaxis) that could be a final judge.
To shorten the post, the comments comes in post #2...
:grad: Knowledge cheats
Proven cheats
Map The AI knows the map even before exploring. This includes the position of your cities.
Unit position The AI knows the position of all units, including barbarians. By knowing this, it also knows the number of units and where there are undefended cities.
Resources The AI is knows where resources will pop up in the future and tries to settle in those areas.
Production cheats
I know no proven production related cheats, although the AI gets cheaper production on higher difficulty levels.
Free of charge
Settlers The AI does not get instant production of settlers when nearby cities are razed.
Military unit production The AI does not cheat by getting extra defensive units for free after having taken a city.
Production without resources The AI needs resources to produce units as expected by the rules.
:love2: Diplomacy cheats
Suspected cheats
Reputation The AI is suspected of taking less reputation hits from breaking treaties than the human player.
Free of charge
Border violation You can move around AI territory exactly as many turns before being forced to leave, as the AI can before you canforce it to leave.
Trade After patch 1.21 the AI-AI trade was exposed in the editor as part of the difficulty settings. On regent and above the AI gives other AI cives better deals, but this is part of the difficulty level you choose. Note that this only means that one AI may sell a tech etc. to a poor AI for a bit less than the calculated price, and the seller will thus loose some money. Also note that the human player is also free to sell to poor AI for whatever cost below calculated, so I don't consider this a cheat.
Movement cheats
No cheats here either, I have even moved the one suspected to free of charge (see next post for why).
Free of charge
Unsinkable galleys AI galleys do not end a turn where it may sink, and therefor cannot cheat in sinkable waters either.
:soldier: Combat cheats
The AI doesn't cheat in combat. Simple as that. There have been some accusations, but those has been proven to be false:
Free of charge
Skewed results The AI does not win more battles than expected by the combat odds.
Vulnerable elite units Elite units are not[/] more vulnerable than veteran units
To shorten the post, the comments comes in post #2...
:grad: Knowledge cheats
Proven cheats
Map The AI knows the map even before exploring. This includes the position of your cities.
Unit position The AI knows the position of all units, including barbarians. By knowing this, it also knows the number of units and where there are undefended cities.
Resources The AI is knows where resources will pop up in the future and tries to settle in those areas.

I know no proven production related cheats, although the AI gets cheaper production on higher difficulty levels.
Free of charge
Settlers The AI does not get instant production of settlers when nearby cities are razed.
Military unit production The AI does not cheat by getting extra defensive units for free after having taken a city.
Production without resources The AI needs resources to produce units as expected by the rules.
:love2: Diplomacy cheats
Suspected cheats
Reputation The AI is suspected of taking less reputation hits from breaking treaties than the human player.
Free of charge
Border violation You can move around AI territory exactly as many turns before being forced to leave, as the AI can before you canforce it to leave.
Trade After patch 1.21 the AI-AI trade was exposed in the editor as part of the difficulty settings. On regent and above the AI gives other AI cives better deals, but this is part of the difficulty level you choose. Note that this only means that one AI may sell a tech etc. to a poor AI for a bit less than the calculated price, and the seller will thus loose some money. Also note that the human player is also free to sell to poor AI for whatever cost below calculated, so I don't consider this a cheat.

No cheats here either, I have even moved the one suspected to free of charge (see next post for why).
Free of charge
Unsinkable galleys AI galleys do not end a turn where it may sink, and therefor cannot cheat in sinkable waters either.
:soldier: Combat cheats
The AI doesn't cheat in combat. Simple as that. There have been some accusations, but those has been proven to be false:
Free of charge
Skewed results The AI does not win more battles than expected by the combat odds.
Vulnerable elite units Elite units are not[/] more vulnerable than veteran units