I was looking at my copy of the D&D Rules Cyclopedia the other day, and trying to think of a way to expand the selection of weapons available to the various classes. I understand that D&D, at least in that incarnation, is to a considerable extent a game of playing archetypes. At the same time, as a guy who understands the urge to do something that just looks cool, I came up with a simple houserule:
Any class can use any weapon, but if it's not on their list of allowed weapons, it inflicts either the damage listed for the weapon, or their class hit die in damage, whichever is lower.
This allows you make that sword-swinging wizard you always wanted to play - Gandalf used a sword, right? - without stepping on the fighter's toes. Your magic-user can use that sword (or battleaxe, or glaive-guisarme, or whatever) as much as he wants; it just inflicts 1d4 damage instead of the damage listed.
It's a pretty sloppy solution, and one I'm not entirely happy with, but if you're dead-set on making a sword-swinging magician, it allows you to do so. I think I prefer this "damage cap" to dealing with the attack penalty ascribed to using weapons not normally allowed to your class. Still, if I was really going to start gutting the Rules Cyclopedia, I'd probably do a full-scale overhaul of the way classes use weapons, based on the weapon mastery system.