Just a summary from some of the great posters here.
ARCHETYPES
Some archetypes that fit the D&D mold and would word as subclasses, with examples:
Barbarian Transformer: "tooth and claw" physically transformed when raging. Goes back to the original Norse ber-serkir who where believed to literally transform into bears. In literature, Beorn in The Hobbit and Barak from the Belgarian series.
Bard: college with access to druid spell list. Goes back to 1st edition, which in term goes back to the Victorian reinvention of druids, and the myth of Taliesin.
Sacred Fist: Monk + 1/3 divine caster. Friar Tuck
Rogue Dungeon Delver: Traps, hazards, etc. Indiana Jones is the ur-example of this, but the expert comes up regularly in various novels and movies.
Rogue Enforcer/Thug: STR based. Many, many examples.
Monk Opportunist: Improvised weapons, use of terrain as weapon, etc. Jackie Chan. Too bad the drunken master didn't cover this.
Pugilist/Brawler/Martial Artist (STR based) - Fighter or Barbarian? Very many examples.
Witch - Warlock? Druid? Wizard?
D&D-ISMS
Some D&D-isms, that we don't have examples but seem like a good fit considering what is currently available. Took out some examples that could already be built like bounty hunters or fighting bards or didn't fit the subclass types we have - for example any sorcerer that was about what the sorcerer did as opposed to it's origins.
Bard
Jester (there is an Unearthed Arcana)
College of Hymns/Hierodule - divine
College of Dirges - necromancy focused. Ouija Board the Necrodancer.
Cleric
Domains: Chaon, Sea, Trade, Love/Passion, Travel
Vow of Peace (though may not make the best adventurer)
Druid
Warden: Plant druid, shape shift in a tree, extra attack at 6.
Herbalist: Does things with herbs (like natural alchemist?)
Circle of Stars: Astrology/Divinination focused. Mystics who read the stars for omens. Illusion?
Fighter
Weapon Master/Sword Saint
Tactical/Cerebral - INT secondary
Paladin
Witch Hunter
Undead/Vampire Hunter
Arcane (gish)
Oath of Liberty/Freedom (Holy Liberator)
Oath of Inquisition
Rogue
Trapmaster: set and disable special traps, thrown oil/caltrops/flasks of oil, etc. Fred Jones, Mystery, Inc. This might also include demolitions / sappers.
Shadow Dancer
Sorcerer
Abhorrent/Aberrant - H. P. lovecraft/far realms inspired.
Warlock
Pact of The Ancient Dragon
Pact of the Genie Noble
Instrument Pact Boon
Wizard
Alchemist (though covered by Artificer)
Wu Jen
Generalist (not an archetype, but it came up a lot that people wanted it)
CLASSES
There were a few that were likely their own classes instead of a subclass:
Shaman / Spirit Shaman
Warlord
Pet class
Psionic - may (should?) also include some subclasses
Summoner
Non-armored Divine Caster/Holy Wrath
There were a bunch of other suggestions without description, like names that may have been from earlier editions of D&D but with no description, etc. Others seemed more like non-mechanical reskins of existing classes like casting via runes could be a wizard or artificer.