Oh, and I've seen some crazy house rules.
--One game I was in, you only got one character, not for the campaign... but FOREVER. If you died you were never supposed to play D&D ever again.
--A Sci-Fi one where the players argued to follow the book when the GM was trying to keep his players alive. The rulebook claimed that their guns did x100 damage while they wore armour that only gave about sixty hit points. We were about to try and bust out of a prison... It would have been ugly.
--Barbed arrows do 1d6 going in, 1d6+2 coming out. The GM thought this made sense and then was shocked when everyone decided to play a ranger... Go figure.
--A GM I had created an artifact in the form of a dagger that kicked you out of his campaign if you were killed by it. He claimed it drank the soul that moved between characters, which also explained why new player characters were so similar to the one's that just died.
--fireball and lightning damage "bounced" off nearby walls. This led to my group using Otiluke's Spheres on big enemies and then dropping lightning bolts inside for 80d6 damage.