The Elder Scrolls IV: Oblivion Glitches

Easy Money - Item Duplication
400 Coins
Access to the Wind Cave (Located Southwest of Weynon Priory)

Go to Wind Cave and explore it. In one of the first chests you'll find there is a piece of clothing worth over 2000 gold! Take it and exit the cave. Travel to the Imperial City's Market District and find "The Gilded Carafe," a alchemy shop. Speak with the shop owner and use your speechcraft ability to get her to like you. Then, look through her inventory of scrolls until you find one that she has 16 of. Buy all of them (if you negotiated low enough it should equal around 400 coins total for all of them). Exit the shop.

Next, go to "Three Brothers Trade Goods" in the Imperial City's Market District (when you exit "The Gilded Carafe" take a left). Once inside, go to your inventory and scroll down until you get to the 16 scrolls you just purchased. Double-click on them and then scroll up until you get to the cloak you found in the Wind Cave and drop it. When you exit your inventory instead of there being one cloak (I forgot the name of it sorry) on the ground, there will be 16; each worth 2000 gold! Talk to one of the shop owners and use your speechcraft and merchantile skills to get him to like you. Then, negotiate with him until he agrees to pay you 1000 gold per cloak (the most he can pay for anything). You'll have to sell each cloak individually but, for the gold, it's worth it. After you do it enough times, you'll have 100,000 gold in no time; enough to buy almost every house in the game!
NOTE: Save one or two cloaks for later so you can duplicate them again. Also, this trick will only duplicate items up to 16 (the number of scrolls you have) so, let's say you have 5 cloaks in your inventory and you do this trick. There will only be 12 cloaks on the ground when you go to pick them up because (4 remaining in your inventory + 12 duplicated items = 16). This trick can also work with any other scroll so long as you have two or more of the same scroll and so long as they are not stolen.