Most recently, Prototype 2, once I maxed out health regen, jumping, and became bulletproof I literally just flew around slaughtering people, and on the odd occasion someone managed to hit me with a rocket I just ate them or waited 10 seconds to get the health back. But my favourite is my Nord with full heavy armour skill, full two-handed, full smithing, and Daedric armour with dragonbone weapons, there are several enemies that cannot do any harm to me, not even a single point of damage.