Fighter
Defined by: Heavy weapon, heavy armor; frontliner; tough; no magic / supernatural abilities
In D&D: Fighter
Examples: Regdar (3rd ed), Siris (Infinity Blade); Tidus, Auron (FF7)
Warlord / Marshall
Defined as: More intelligent / charismatic variant of the fighter; leadership ability; capable melee combatant
In D&D: Marshall (3rd ed), Warlord (4th ed)
Examples: Roy (OOTS)
Big Guy
Defined as: Massive frame, big weapon, slow, but hits very heavy
In D&D: race rather than class - Half-Giant, Goliath
Examples: Hagrid (Harry Potter), Chewbacca
Swashbuckler
Defined by: fencing weapon; light or no armor; mobile; acrobatic fighting style; taunts
In D&D: Swashbuckler class, Fighter variant
Examples: D'Artagnan (3 Musketeers)
Thief / Rogue
Defined by: Sneak attack; stealth; traps and locks; acrobatics; skill monkey
In D&D: Rogue
Examples: Haley (OOTS)
Adventurer
Defined by: Everyman who gets caught in the story; luck; big heart; resourcefulness; grows to become larger than life
In D&D: Commoner (if it was more heroic)
Examples: Everyman hero (Feng Shui RPG); Frodo (LOTR); Twoflowers (Discworld), Tourist (Nethack); Abenteurer (Das Schwarze Auge)
Bard
Defined by: Music-based magic; social skills, thievery and deception; swashbuckling fighting style
In D&D: Bard
Examples: Elan
Archer
Defined by: Bow; Can be soldier type, wilderness-oriented, sneaky type or arcane
In D&D: Ranger, Fighter variant, Arcane Archer PrC, Elf
Examples: Thief PC game, Kagome (Inuyasha), Legolas (LOTR)
Barbarian
Defined by: Rage; big and tough; 2h weapon or dual wield; wilderness skills; light or no armor
In D&D: Barbarian, Warden
Examples: Conan
Wizard
Defined by: learns spells from books; powerful magic effects; starts weak and becomes invincible; magic school variants
In D&D: Wizard
Examples: Raistlin (Dragonlance), Gandalf (LOTR), Black Mage (FF), Harry Potter
Sorcerer / Witch / Warlock
Defined by: Source of power, either innate (dragon blood etc.) or outside (pact with dark entitity): spontaneous caster
In D&D: Sorcerer, Warlock
Examples: Hennet (3rd ed), Esme Weatherwax / Nanny Ogg (Discworld)
Arcane / Divine Trickster
Defined by: thievery and social abilities as mix of skill and spells
In D&D: Rogue / Wizard, Beguiler (3E), Arcane Trickster; Cleric of Vhaeraun (and similar deities)
Examples:
Druid
Defined by: Nature-based magic; summon animals; healing
In D&D: Druid
Examples: Merlin (Arthur legend), Druid (Diablo)
Shapechanger
Defined by: Change shape into a powerful combatant, such as Werewolf
In D&D: Druid, Wizard (build option)
Examples:
Summoner
Defined by: Summon powerful creatures to serve you on the battlefield
In D&D: Cleric, Druid, Wizard (as part of their abilities)
Examples: Summoner (FF)
Red Mage / Gish / Bladesinger / Psychic Warrior
Defined by: Sword and sorcery - magic-infused weapon attacks and self-buffs; light armor; variant: psionic
D&D: Swordmage (4E), Bladesinger (AD&D), Duskblade (3E), Psychic Warrior (3E), Fighter / Mage
Examples: Red Mage (FF)
Psion
Defined by: Weak body, strong mind; telekinesis; telepathy; mental attacks
D&D: Psion
Examples:
Necromancer
Defined by: Summon undead; poison; bone spells
In D&D: Wizard subclass or Cleric variant, Dread Necromancer class (3E)
Examples: Necromancer (Diablo)
Paladin
Defined by: Knight with divine powers; healing; smiting; heavy armor; mounted combat; Code of honor
In D&D: Paladin, Cleric, Runepriest (4E)
Examples: Crusaders (history), Miko (OOTS)
Black Knight
Defined as: Fallen Paladin; Knight with necromantic, demonic, or generic "dark" powers; Anti-hero
In D&D: Blackguard
Examples: Darth Vader
Priest / White Mage / Staff Chick
Defined by: Robes; healing magic; party buffs; light-themed offensive magic; turn undead
In D&D: Priest (AD&D Cleric variant); Invoker (4E)
Examples: White Mage (FF)
Monk / Martial Artist
Defined by: Melee combatant; Asian theme; mystic powers (Ki); unarmed; "monk weapons"
In D&D: Monk
Examples: Feng Shui RPG; Crouching Tiger, Hidden Dragon / Wuxia movies in general
Artificer / Alchemist
Defined by: Channels magic through items
In D&D: Artificer
Samurai
Defined by: Japan theme; melee combatant / archer; Warrior code
In D&D: Samurai class
Ninja / Assassin
Defined by: stealth; poison; mystic powers (unlike rogue); often Asian themed
In D&D: Assassin, Ninja
Examples: Ninja Gaiden (video game), Assassin guild (Discworld)
Pirate
Defined by: seafaring skills, fencing, devil-may-care attitude
In D&D: surprisingly unserved, except as some PrCs
Examples: Jack Sparrow
Ghost
Defined by: immaterial undead, often left behind because of some unfinished business in life
In D&D: template in 3E
Examples: Ghost (Feng Shui RPG)
Vampire
Defined by: undead, sucks blood, weakness to sunlight and other things, mystical powers like turning into bat
In D&D: template (3E) or class (4E)
Examples:
Comic Relief
Defined by: Tag-along character; either comically incompetent but very lucky or comically powerful, or hypercompetent in some niche; serves to lighten the mood if things get too grim; often plucky or scrappy
In D&D: Kender (implicit)
Examples: R2D2 + C3PO; Richard (LFG); Belkar (OOTS)