Ok, sorry if this have been posted before, but I did a search and found nothing.
This has no use whatsoever, it is only a fun novelty but here it is:
Go to Bom'Bay in Sen'Jin Village (Durotar). He has a quest for around level 5, not sure exactly though. Complete this quest then return to him. When you talk to him again you can click several various chat links. It doesnt matter which one you click it gives a completely random result. The random buffs are:
Turn into a snake for 15sec
Drunk affect for 5min
Grow very large for 5min
Turn into a chicken for 15sec
Turn into Ghost for 1min
Thrown into air
Ok so here is the exploit, keep talking to him until you get the buff "Grow". Once you have this log out then log back in again and keep talking to him again. This time, instead of simply renewing the buff, it will apply another buff, stacking with the old one.
Remember, this buff only stacks twice but the effect is more than satisfactory
This buff also stacks with the "Winterfall Firewater" buff, so get some of those too if you want to get even bigger