A cool feature would be the addition of a leveling weapon, item, or armor that would gain experience with you as you fight. Fighting with various weapons as a player I get attached to a weapon and would like it stay with me since it was my partner that has lead me to slaughter thousands of foes.
Say you gain just a normal longsword or knife whether it be from a corpse or a shop, but seeing it you know it to be the weapon for you. It protects you, your friends, family, caravan, slays your enemies, fights with you through starvation, thirst, wars, disease. You name this weapon with a word/words that give its purpose at your side meaning beyond just being a tool. It is your true friend, ally, and even your bitterest enemy. As you live and fight it takes on a personality of its own gaining power from your ability, will, and knowledge. From gaining the ability to freeze an enemy in place with fear from the blood still rolling down the blade to an edge honed to perfection through considerable care and sharpening, to even giving a faint light of hope to all that surround you this weapon is would be your legend one which future adventurers, cults, and kingdoms would fight to possess. For this blade is the true "Lord of Murder's" legacy.