While Fishing outside of the Violet Hold in Dalaran, you can get a Rusty Prison Key.
When you use the keys on a footlocker nearby, you will get one or two rares, and some potions and vendor trash. The blues can be sold for upwards of 100-200 gold.
I get about 1 key every 15 minutes or so. I can make around 800g an hour with this.
You need 430 fishing to fish, and 525 to fish without interruptions. Good luck
by Diabloss39