Armor and Weapons: Damage reducing armor, Archery rules, Handedness rules, Encumbrance, Two Weapon Combat, Arrows and Ammo. Deceptive Equipment (the deceptive equipment was good for one adventure and then went in the dust bin).
Mini-games: The Indiana Jones-like chase rules. Largely non-lethal, good for getting the mechanics of die rolls down and escaping combat while still getting the sense of risk.
Quick unarmed combat for AD&D and B/X. Avoids grappling, etc.
Standard Character Sheet for AD&D, this is my classic AD&D character sheet available which incorporates Unearthed Arcana. It is available at DriveThruRPG.
Professional Skills and NPC Skills, this is my book Zero to Hero: Uncommon Commoners, also available at DriveThruRPG.