Summon A Shark, Kill Your Friends... (Patreon)

If you fish in a region for "Black Baracuda", which are most populous off the Suramar coast but can be found everywhere in the Broken Isles, you will occassionally receive an item called "Stunned, Angry Shark". 

When you "use" this item a shark mob will appear in the nearby vicinity. 

Because this is an inventory item, albeit with only a 1-minute duration, you can port anywhere and use it to attack nearby players. The shark has 2m health and is surprisingly tough.

The shark also drops "seabottom squid" which sells for 10G a time, and can also be used to level fishing skill by 5.