Following up on my earlier thoughts on character classes and skills, I've been trying to come up with a list of character archetypes that a game would absolutely need, and I'm coming up against a wall. There either seem to be way too many such archetypes (in which case I suspect I'm defining the term too broadly and letting in too many specific sub-types) or I end up narrowing it down to two (in which case I am certain I am not allowing enough specificity).
A bit on sources might be appropriate before delving in too deeply. D&D naturally draws on swords-and-sorcery style fiction as a chief source of inspiration. That genre has its own set of archetypical characters that a game could (and should) draw on. We have Conan, Fafhrd and the Gray Mouser, Elric, Prince Vakar, Thongor, Cudgel the Clever, Rhialto the Marvelous, etc.
An interesting point; looking back at that list of names, all but one is a warrior-type (and I might argue that Rhialto was deliberately written to invert the trope of warrior-as-hero). Wizards-as-heroes seem to be very much under-represented in the genre. The Gray Mouser dabbles slightly in such stuff, but his real claim to fame is as one of Lankhmar's greatest swordsmen and burglers. Elric, too, is much more often seen with sword in hand rather than conjuring some awful magic. I'm doubtless missing a few counter-examples, but I think it's safe to say that in terms of archetypes, the warrior is much more often the protagonist, and the wizard is most often cast as the villain. (Even in Tolkien, the Fellowship is, essentially, a warrior-band; Gandalf, while present, hardly uses his magical powers throughout the entirety of the LotR).
Mythology (and mythologized history) also has quite a bit of influence on D&D. Arthur, Lancelot, Robin Hood, Rolland, Sigurd the Dragon-Slayer, Hercules, El Cid, Merlin... Again, the warriors are vastly over-represented compared to the magicians. I might go so far as to say that there are indeed only two archetypes within this broad spectrum; the wizard and the warrior (although there are vibrational echoes within the warrior archetype; the warrior-as-thief, the warrior-as-king, the warrior-as-pirate, the warrior-as-mercenary, etc.), and the wizard-as-hero is a theme seen so rarely as to be remarkable when it does appear.
However, it should be noted that fantasy RPGs have, over the last thirty years or so, developed into a literary field of their own. And as such they have developed their own internal archetypes. The thief, the cleric, and the bard have, simply by virtue of being included as "primary classes" (in the case of the bard, as of 2nd edition AD&D), have become archetypes alongside the warrior and the wizard. At least within the sub-sub-genre of fantasy RPGs.
But I wonder if this doesn't work out after all. What is a thief, but a lightly armed warrior who can pick locks? What is a cleric, but a warrior with healing magic? The bard is a warrior with magical powers of a different sort. In fact, the only class that doesn't qualify, at least on some level, as a warrior... is the magic-user.