(Psi)SeveredHead
Adventurer
Damage reduction based on a certain +X feels metagame-y and the numbers were so extreme it made the monsters unbalanced. The older monsters you couldn't damage at all were even worse. The /magic (and /metal or /alignment) DR system was by far the most dynamic, intuitive, and balanced.
This.
The only bad part was some devils had ridiculous regeneration (they regenerated anything that didn't come from a holy silver weapon, which meant no amount of magic, not even alignment blasting spells, could kill them). But really, that was my only complaint.
I never saw the golf bag of weapons. -10 damage wasn't too much. -30 damage, on the other hand...