Duping any item

Step 1 - Drop anything you want to dupe on the bed where you start off
Step 2 - Save, and load the file
Step 3 - Pick up all the items that were on the floor at the bed
Step 4 - Defeat Chaos and watch credits (long part here)
Step 5 - Load file again, you should have all items in your inventory + the same items on the floor

Hold more than 100K gold in each "bag"

You are gonna have to have alot of gold for this one, check the glitch for multiplying gold.

When you die, you will unequip an armor, drop it, and drop HALF of your gold in 1 Pile.
So, if you have lets say, 500k with you, if you die, that will turn into 250k in 1 Bag!! Whats the advantage of this you say? Well, if you can hold more than 100k in each bag, that increases your total you can hold in your bank! The max in 1 gold pile is 1.25 million, which is made when you have 25 bags of 100k in your inv when you die. This increases your total from 7.5 million (100,000 per bag * 15 spaces in bank * 5 spaces of 15) in the bank to 93.75 million (1,250,000 per bag * 15 bank spaces * 5 screens)

These results are only with 100k of gold. If you want a HUGE PILE of gold, use a few piles of 1.25 mill, so you could make a pile of 15.625 million gold. Then 195.3125 million, and so on.
READ THE CAUTIONS.

*CAUTION!!!
-Having more then 1million in a bag may be dangerous, I am not responsible for erased characters or such. I'm not sure if it could happen, but I'm not gonna test it, it's up to you from there . If you only have 1999998 in your inv when you die, you will get a pile of 999,999 gold. That should be safe.

-I'm not sure what happens if you manage to get more than 9,999,999 in the bank, please be careful.

Multiply money

First, have over 100,000 gold in your bank and inventory combined.
Next, put any amount of money into your inventory.
Finally, grab the money in the bank and drop it on the money in your inventory. Make sure the total will exceed 100,000.
When you do this, the bag that had the lowest amount of money will be duplicated. A new bag of money will appear with that amount in it, the bag that was originally in your inventory will have 100,000 gold in it, and the money from your bank will still be in your bank.
This will not work if there is a money bag in your first two item slots. Also, whatever is in those slots will be replaced with the money.