Ah, the memories! Our group of enthusiastic @13-15 year olds got the bright idea to use a dirk of doubling to make sure we never ran out of ammo. Our poor inexperienced DM let us browbeat him into allowing it and from then on we were pretty invincible. After a while the DM picked up "Deities and Demigods" and got his revenge on us.
We had similar fun with a scenario from a company called "Role Aids" based on the movie "The Keep".