In Fable 3 for the Xbox 360, there is a way to essentially get an unlimited amount of gold fairly easily by using the item duplication exploit. This can take your gold up very high extremely quickly.
Start a coop game, and have player 1 go up to player 2 and press LB to go to the gift room. Give them all of your gold pieces, 100,000 at a time per gift, and then press start to exit
Have player 2 press start to go into the Sanctuary. Have them go to the gifts and reject all the gold, then press start to leave the Sanctuary, and exit the coop game.
Now player 1 presses start to go into the Sanctuary and receives the rejected gold. When player 2 joins again and goes back to the Sanctuary, and the gold will still be there for them as well.
To keep this loop going, have player 2 reject the gifts again to keep having them sent back to player 1 over and over again.
Please note that this has been patched, so avoid updating the game if you plan to use this method of duplication.
