• Eliminate spellcasting per se, but allow crafting of scrolls, potions, etc. (Oriental Adventures "re-skinned" scrolls as talismans.)
d20 Modern does that as well.
d20 Modern originally came with three campaign models; one of which was Urban Arcana, with the 10-level advanced classes to basically replicate a truncated wizard, psion and cleric. Shadow Chasers, which was more
Buffy or
Supernatural like had a "spellcasting" advanced class that basically just used Use Magic Device along with scrolls, wands, and whatnot.
Curiously, while reading over the Pathfinder version of the Rogue, for an all-rogues game that I'm going to run, I noticed that they've added some additional Rogue talents above and beyond the 3.5 version of the game that would allow Rogues to be spellcasters in this manner--including having 0-level and 1st-level spells as a class ability, and a familiar. This really appealed to me as a substitute for spellcasting classes altogether in a low-magic game that could feel much more sword & sorcery-like; in fact, I was immediately struck by the resemblance to the source material for the rogue, particularly the Gray Mouser.
And then, of course
d20 Modern had Agents of PSI and Gene-Tech (the latter of which was cut from the book itself, but later released in Polyhedron) that didn't have any magic at all; Agents of PSI, obviously have psionics, and Gene-tech not having any supernatural at all.
d20 games like D&D or d20 Modern are certainly very playable without access to magic, or with reduced access to magic, and doing so can focus them more on being swashbuckling, or horror, or intrigue, or, I dunno, bringing out conventions and tropes of all kinds of other genres. As well, frankly, as more closely resembling much fantasy fiction, where something like the wizards of D&D are usually fairly rare.
I find that for my tastes, even E6 alone isn't enough limitations on magic--from a
setting aesthetic perspective, mostly. Some of the third level spells, like
speak with dead means that 6th level characters, assuming that one is a cleric, can't ever do a fantasy murder mystery without shortcutting the entire thing, for instance.
I freely admit that my desire to limit and reduce magic is a quirk of my own, however, and is possibly quite esoteric in relationship to other gamers who are more comfortable with the implicit D&D assumptions. And I'm not sure that I have a "favorite" solution to that particular problem.
But certainly the
simplest one is to make the game E6 and arbitrarily say that characters can't take any spellcasting class levels until they've already taken a couple two or three levels of something else.