I've got more variant rules ideas than I really know what to do with, or will ever get to test in a reasonable amount of time. Still, I'd like to throw some of them out there and see what people think of each one- either independently or not.
Bleed damage stacks up to the victim's normal Constitution score. If it doesn't have one but can somehow still Bleed, it can stack as if the being had a score of 10.
Effects that cause a variable amount of bleed damage roll for their amount once, not per round. The amount rolled is added to the total.
Magical curing effects, Fast Healing, and Regeneration only stop an amount of Bleed damage equal to the amount of HP healed.
Magical effects that do nothing but stop all Bleed instead stop an amount equal to their effective Caster Level immediately, then once more at the beginning of the next round.
The Heal check DC to prevent someone from taking Bleed damage is set to 10. If the person performing the check is using Heal untrained, if they make a DC of 12 or greater, no Bleed damage is taken that round and the total ongoing Bleed amount is reduced by 1. If Heal is a trained skill, the amount of ongoing Bleed suffered is reduced by 1 point for every 2 points above DC 10 on the check result. A person can try to stanch their own bleeding as a move action.
(This was born out of a desire to change the way the Rogue's sneak attack worked)
People treat magic like physics on demand. If you embrace this paradigm, then you would probably agree that there are multiple methods for reaching the same end result of "Fireball."
Spells are spells. Their effects can be achieved using multiple schools. Instead of re-listing an effect in multiple schools as different spells with cosmetic differences, a spell that could be cast different ways gains the most appropriate school as a descriptor. Feats and specialties that operate based on school apply to spells when they have that descriptor. A spell that has a specific school as a descriptor must follow universal rules of that school (such as Conjuration's rule of requiring a surface capable of supporting anything conjured, or Abjuration spells interacting with each other or breaking if forced against a being).
Examples of spells with multiple potential schools: Cure Light Wounds (tradition Conjuration, Evocation, or Necromancy), Fireball (Conjuration from the plane of Fire or Evocation), Phantasmal Killer (Illusion, Enchantment).
It is possible that re-classified spells have minor differences. A Conjured Fireball might require a flat, unoccupied surface 5 feet across to be cast, but ignore SR.
Since this weakens the drawback of Prohibited Schools, it is encouraged to either extend the -4 penalty to all skill checks involving Prohibited schools or drop the extra spell provided each level for Specialists (the school boons of specialists would still be granted).
Rugged: The weapon has a well-deserved reputation for being able to function despite casual abuse, mistreatment or minor neglect. This can be because of robust design, excellent crafting, high-quality materials or any combination thereof. Whenever the weapon must make a Fortitude save (be it weather, a special attack, magic, or an inherent failure chance), it gains a +2 inherent bonus to that check. Its Break DC is two points higher than normal at all times. The weapon also has extra overall hit points: one extra for Fine or smaller objects, two for Diminutive, Tiny or Small objects, and three for Medium or larger. Long-term neglect, such as never cleaning the weapon or years of exposure, may eventually negate this quality or even replace it with Shoddy.
Shoddy: The weapon is a particularly poor specimen of its type. This can be because of flawed design, a lack of maintenance, poor crafting, substandard materials, or some unfortunate combination of the previous. The weapon has its Break DC lowered by two points, a -2 inherent penalty to Fortitude saves, and fewer hit points than normal (always to a minimum of one hit point): One less for Fine or smaller objects, two less for Diminutive, Tiny or Small objects, and three fewer for Medium or larger. Some ceremonial weapons, designed to be more decorative than useful, fall into this category.
Close-Quarters: Ranged weapons with this quality were designed to be used at short range, usually in cramped spaces or other situations where an enemy can suddenly close in. They do not provoke an attack of opportunity when fired at an opponent in melee range. Any reloading still provokes an attack of opportunity as normal.
Regional: The weapon is only found in a few select areas or cultures, and those outside will not be familiar with its specific nuances or full capabilities without tutelage or an inordinate amount of experimentation. These include the atl-atl, broadsword, katana, kukri, kunai, rapier, shuriken, tonfa, and pilum among others. The weapon type is excluded from general proficiencies granted by levels unless the character in question hails from/was trained in the appropriate region. Full proficiency can be gained normally via bonus feats, Deity favored proficiency, or RP methods approved by the GM.
(the last would likely need a change in the "Weapon Proficiency" feat to be that workable- something like the ability to gain 4 weapons with Weapon Proficiency instead of one. I always liked that idea anyway.)