...other than obvious - sword, bow, punching.
For example, the wiki has an entry on Zombie Pigman:
2.5% chance to drop a gold ingot if killed by a player
8.5% chance to drop their golden sword when their death is registered as a player kill. The chances of each can be increased by 1% per level of Looting.
Zombie pigmen drop 5 experience (12 if baby), when their death is registered as a player kill.
I know there exist pigmen-based XP farms that don't involve the player attacking any pigmen directly. So what sort of deaths count as 'player kill' for the purpose of loot/XP drop? - at least from the more common/practical ones... I'm well aware there are hundreds of ways one can kill a mob.
(if you have the extra knowledge about how these affect pigmen hostility; in particular if any drop XP but don't make zombie pigmen hostile, that would be a nice addition to the answer.)