A collection of house rules for armor protection (versus different types of damage), armor durability, repairing armor, critical success and "radical" failures (both with result tables) for combat and skill checks, and called shots. The cover claims these can be used for any system, but they seem to be built around the d20 system.

The layout for this PDF is a little rough and there are more than a few spelling and grammar errors, but perhaps that is in keeping with the "hardcore" theme. If you are interested in paying for someone's hastily scribbled house rules, you might like this PDF.