I've run across some odd 'flavor' house rules, like:
1. All magic is evil, and eventually only evil comes from it. (Ah, so the CLW spell you just did will eventually come back to haunt me? Ooookay.)
2. All magic is good, and evil spellcasters eventually are dealt with by it (why are we adventureing, again?)
Oh, here's a bizarre one.
Dragons are sources of primodial might. They are power incarnate. And they are apparently delicious.
Being power incarnate, some part of a dragon holds that power within itself, be in the blood, the bones, the teeth or the heart. Indeed, any part of the dragon from it's liver to his eyes could hold its power and lucky is the adventurer who finds said part and consumes it, for they gain some permanent ability.
This led to us hunting dragons, blowing them out of the sky, then literally leaping upon them to discover what part of this particular dragon was magical. Then fight over who go to consume what. This led to such glorious exclamations of valor as 'It's in the heart! The heart!' - everyone dives for the poor beasts heart, carving chunks of raw dragon and bolting them, then waiting for the effect to take place. 'Wow, I can see in the dark!' or 'Man, I'm a lot stronger all of a sudden'.
Not so much an eye-rolling terrible rule, but man was it funny.
More to come as I remember them.