CombatEventsCore implements new Combat-centric events for plugins that need to track Combat more heavily:

Currently there are 3 new Events:

EntityKilledByEntityEvent
PlayerEnterCombatEvent
PlayerLeaveCombatEvent

CombatEventsCore comes with a few of it's own configuration options:

Camper Detection
Combat Time
Combat Entrance/Leave messages
Allowing Tamables to put a player into combat
Allowing enemies that target a player to trigger combat.
Deny certain commands while 'in-combat'