Duping is the most sought offered exploit in all MMO games. Currently available are three dupes that will help you dupe items, gold or equipment. These are hard to find, so when they are found, they will be nerfed soon. These dupes are easy to use and can help any character duplicate any item they need. Even with these dupes found out, more are often found out as quickly as possible. Final Fantasy XI's biggest gold dupe was the mog house dupe where players would insert gold into their mog house then quickly log off and back on. If it was done correctly the player would have actually have duped all their items and gil inside of their mog house thus giving many players a giant advantage of everyone else However this dupe was quickly nerfed and a good amount of players where banned from it.
Here is an example of FFXI Dupe Final Fantasy XI Dupes Information submitted by our community in the past. (Note this information is not valid and should be considered nerfed)
People have been asking for this, so here it is.
This is the latest AllWait0 that ive found. Ive only had a sec to test it
and it worked on the AH. However, i didn't check with anyone around me to
see if it shouts. Therefore I leave that responsibility up to you, should u
choose to use this. Im sure people will post their experiences with it here,
so eventually it will either be proven safe, or unsafe. Ill remove of course
if its unsafe. Nothing gives me that impression so far though.
EDIT: Seems most people agree this version is clean/shout free.