Don't get me wrong, I intend to play Pathfinder as is. I even plan on keeping their combined skills rather then using the ones my groups have been using since 3.0. There are a couple of rules that I've wanted to try out since late 3.5 that I never got to try do to the rift that developed between one group about 3rd vs 4th. I also wanted to see what PFRPG did. I still want to give these a shot at some point:
Damage Threshold: Replaces DR. DT services as a pool of hit points that refreshes each round. The idea is to keep monsters tough, but allow even a wizard with a dagger to contribute to a fight and avoid having the sword caddy. The formula I was thinking of was DR/5 x (CR + Size). Large = +1, Huge= +2, etc. I'm also toying with adding Natural Armor and/or Con bonus to the total. I was thinking that, instead of bypassing DT, anything that would normally bypass DR would add an extra 1 or 2d6 to the damage. I was thinking of giving Barbarians 5 DT every time they would have gotten DR 1/-.
Variant to Attacks: First of I want to state that you get your full BAB on each attack. I've had people nearly rip my head off before I finished because they thought I was nerfing fighters. The idea is that, as you progress, you gain an attack based on your Standard, Move, Swift, and even Immediate Action. Rapid Shot, Flurry, Two Weapon Fighting, etc. give you an extra attack if you take a Full Round Action to attack. I originally invisioned having the extra attacks be based on feats. The idea is to give fighter types the ability to dish out damage even when they have to move and to cut down on the time it takes high level fighter types to take their turn with all their attacks and various bonuses.
Any one else have variant rules they want to try out?