None in 3.5, and I had ONE in 3E: Rangers can use their virtual Two-weapon fighting with double-headed weapons as well as two weapons. That was not only my most trivial house rule, it was my ONLY house rule.
It's something that John Tweet said was technically not permissible in the RAW, but he'd allow it if it were him.
This is one of the best house rules ever. I plan to do the same with the more complicated buff spells (like divine power, righteous might, etc). If you don't have your modified stats worked out beforehand, don't even bother memorizing it.
You may draw, load, and fire a light crossbow in a single round, as a special full-round action. If you attempt this and roll a natural 1 on your attack, you have shot yourself in the foot.
The Decipher Script skill is necessary for the translation of heiroglyphs – on top of speaking the language. The average Khemitian is no more able to read heiroglyphs than the average medieval peasant could read the Latin mass. Decipher Script is a class skill for Khemitian priests.
The only house rule we have is that Hit-point dice are rolled by the player and secretly by the DM. If the player doesn't like his roll, he takes the DM's roll, whatever it is.