The following house rules have been used by our game group for several years.
Autofire - a more realistic, and quicker, method of handling automatic weapon fire.
Hit Locations By Damage - a system for determining the hit location of a wound based on the amount of damage points inflicted. It also includes detailed rules for describing wounds and treating them.
Shooting Modifiers - additional modifiers for shooting over those used in the Call of Cthulhu rulebook.
Action Order of Declaration - a method for determining the order in which players declare their character's actions each turn.
Character Generation - a method for generating, based on the method recommended by Pagan Publishing characters.
Competency - a method of determining a character's competency based on his skill values, plus how to use this information.
Difficulty Modifiers - a system for modifying skill percentages based on the difficulty of the skill. It includes specific modifiers for Hide, Sneak, Spot Hidden, and Track skills.