I've only got 2 "house rules" though they have nothing to do with game mechanics, and we only use them in one of my two campaigns for now, where I had to address specific issues.
First, your PC will not threaten another PC without an extremely good reason. IOW, you won't make a character so unstable that he would threaten or assault a close friend on a whim. Apparently, a couple of players of particularly savage characters (a tauren and an orc) got into their minds that anyone who disagrees with them is dumb and that an attack for non-lethal damage or very little damage is a good way to explain your position. Now, I really like it when people do stuff because of roleplaying. But I really don't like it when people do stuff, and then try to justify it with roleplaying. So that had to stop. You attack a PC, you're being a jackass and you're out of character too, subdual or not.
Second, you have 10 seconds to decide what to do in combat. This doesn't include rolling dice or looking up rules, but it does include talking with the other players. When the time is up, the last action you've declared is what you do, or you lose a round. This because players would chat or read manuals while not their turns, and then when their turn came they would have to be explained what happened, reassess the situation, and then take a decision. And, because one player kept telling everyone else what to do. He's a good tactician, but that doesn't change the fact that discussing every action of every character is an irritating waste of time. I had grumbling from spellcasters, who claimed that you need several minutes to choose which spell to cast and that you couldn't choose it before your turn because even a simple movement could force your whole strategy to change. Since these same players would take 5 minutes to choose what to do even when the situation didn't change one bit from the previous round, I didn't shed a tear.
