All the basics, of course, Cleric, Fighter, Mage, Thief. But I don't mind some variety. In the DD game, I also had available Monks, Rangers, Assassins (although I don't see myself allowing these much) and Fighter-Mages (since I got rid of the racial classes, this is the same as the Basic D&D Elf). I just got the pdf of Joseph Bloch's Adventures Dark & Deep, his alternate AD&D2E, and I particularly like his version of Gygax's Jester class, a Bard sub-class. So I'll probably port at least both of those over, as well as the Thief-Acrobat and Mountebank, and a few others. The Jester is an acrobatic melee and hand to hand fighter that fits much better into the Western European milieu that most settings assume than the Monk, which I've never been particular fond of. It's not identical, but they seem to me to share a similar niche. (If I was to run a more Eastern setting, Monks obviously wouldn't be a problem, and Fighters and Rangers would be replaced with Samurai and Ninjas, etc.) They get some access to spells, as Bards do, as well as a series of abilities separate from but similar to the way Thief abilities work, juggling, knife throwing, that kind of thing. So initially, the list of available classes would be:
Druids and Cavaliers/Paladins are an odd thing to me, I really dig the way DD does them, being alternate classes the Cleric and Fighter can choose later on as they progress in level. I also dig the old Rules Cyclopedia division of Avenger/Knight/Paladin depending on alignment, but there's also something to be said for making them classes unto themselves, the way they already are in S&W. I'll figure out what's easiest and do that.
Along with the standard human, dwarf, elf, halfling, I'm down with gnomes, half-elves, half-orcs, whatever. In fact, a houserule I came up with for the DD game was that any 1HD or less monster race could also be a player character, provided that any special abilities they had weren't much more fancy than that of the standard demi-humans. As I recall, we had a kobold Ranger who was pretty fun. I see no reason to not continue this trend, with GM approval, of course. Since I'm not a fan of level limits for demihumans, I got around the balance issue by giving humans a blanket 5% XP bonus to compensate for their lack of fun stuff like Infravision and such. Since it stacks with the class-based XP bonus for high stats, it seems to work pretty well. I think I stole that trick from Basic Fantasy.
I also had a schtick where all of the characters were members of an adventurer's guild called the IWW - Itinerant Warriors of the World, which had strict non-discrimination policies towards race and alignment, so "monster" races with union cards could remain unmolested in polite society, at least as long as there was a guild house in town. The IWW was there mostly to amuse myself as a non-current member of the actual IWW (Industrial Workers of the World). None of my players ran with it and tried to recruit dungeon dwellers into the union rather than fighting, but the option would have been there, if they tried. In terms of game play, it also gave them discounts on delving equipment and a labor pool of hirelings and henchmen to choose from, and a reason why such would be available.
More musings to follow.