The Elder Scrolls IV: Oblivion/Glitches

Near-infinite Gold
You can get near infinite gold by finishing the vampire quest, see here for more info. After you complete this, you will be given a leveled gold reward (up to 10,000), you can talk to the count again and again so you can get near-infinite gold. Remember: do not close the dialogue box until you get the desired amount of gold.
 * Note: This has been fixed in the 1.1.511 patch.

Easy Imperial Guard Armor
If you want to get your hands on some Imperial guard armor there are two ways. The first way is to just kill a guard, though it may be best to do this away from the Imperial City to avoid the guard calling for help, and you dying! The second, and by far easiest, way is to go up to Bruma and exit the city from the gate that is up North, and go North-West until you hear a fight going on. Get close to see two Imperial "Foresters" shooting at each other with their bows. Wait until one of them gets killed, walk up and take his armor, easy as that!

Cloning Glitch V.1
Get a bow and some arrows. Then go into First Person Mode and hold the right trigger. Open your menu, and select the arrows twice with A. Then find the item you want, and press X to drop it. Then let go of the trigger.
 * Note: This has been fixed in a patch.

Cloning Glitch V.2
You need some copies of the same scroll. An easy way to do this is to go to the Imperial City Market and buy 16 Absorb Magicka scrolls from the Calindil at the Mystic Emporeum. Open the menu and select the scrolls twice. Then drop the item you want to clone. The item will be cloned a number of times equal to the number of scrolls in the stack. This doesn't work on Nirnroot samples or certain enchanted items.