there are plugins that give you 5 seconds of god when you log in i believe
and there are also ones that kill you automatically if you log out during pvp to prevent cheating
would also work for if you take damage from a mob too
I remember there was one that when you log out, for a few minutes it just left a ragdoll sort of thing in your place. Everything could attack it (And pvpers if enabled), and if you killed it, it dropped player's items (Then taken out of inventory of killed player).
