This is a very D&D-specific question, so my apologies to those of you who play other old school RPGs: how many character classes do you allow in your campaign? Mostly, I'm curious to see how many of us stick to just the three/four "basic" ones (and for present purposes, I'm lumping Moldvay-esque racial classes in with these) and how many allow lots more.
In my Dwimmermount campaign, I began with just OD&D's three (cleric, fighting man, magic-user) and eventually allowed a modified thief as an NPC. I also introduced paladins and planned to introduce druids. In principle, I might allow even more classes if the need ever arose, but, so far, it hasn't and the game is primarily an "original three" campaign that's open to more if the exigencies of play demanded it.
How about you?