ZDoom

I never played Halo so it may be normal, but...
Get shield. Summon cyberdemon. Make him shoot a rocket at you. You may get a corpse with 100% health...

Another idea I had was to even attempt turn based attacks, but I don't think that's possible, and if it is, it'd require a bajillion lines of code. You mean something like that? Don't tell me that it is full of bugs, I know it... Even your health and ammo remain unchanged after the battle. BTW, is ...

Is there any way to change player using DECORATE, or I have to use DeHackEd? Also, is there any Hexen state actions in DECORATE (Something like A_BishopAttack)? I do not see any way to make projectile flying like the projectile of dark bishop from Hexen.