If you throw a snowball at a zombie pigman then let him take environmental damage from falling he will drop XP and give you bonus loot with a looting 3 sword (drop swords and gold bars)
In addition, ALL OTHER zombie pigmen/pigman in the area that receive aggro to you will ALSO drop loot and XP as if you had killed them. This happens no matter how you start the aggro, and due to the new aggro mechanics can go on almost forever allowing you to easily exploit the spawning conditions and aggro mechanics to get a never ending stream of zombie pigmen running at you.
http://gfycat.com/AffectionateActiveAurochs