The Elder Scrolls IV: Oblivion (PC)

Cheat List
Firstly, add a -dev or -devuser switch to the command or target line to the game executable via a Windows shortcut. While playing, drop the developer console via the tilde/~ key (next to numeric 1). 

help - List available console commands
tgm - Invulnerability
tcl - Toggle clipping
lock - Lock highlighted object with integer lock-level
unlock - Unlock highlighted object
kill - Kills highlighted entity (kills self if no target is selected)
modpcs , - Add integer points to skillname skill
modpca , - Add integer points to attribname attribute

Stealing from NPC Shopkeepers
First off, go to any armor shop that has a piece of armor on display that you want. Jump up onto the shop keep's counter and just run into and knock the armor or item you want off the counter. This is not illegal in the make believe universe of Elder Scrolls and it will rouse no undue interest from anyone. Now, you just keep kicking it by running into it multiple times until you have the item in a corner away from the view of the shop keeper.

The shop owner will actually follow you around the shop while you run about. Get him/her to follow you to the opposite end of the store, then quickly run back to where you placed the armor item. Use the sneak ability (default RIGHT CTRL) and pick it up before they see you. If you are good enough, you can steal armour and maybe more!