Remember that one kickass fencing scene from The Princess Bride where Wesley and Inigo Montoya duel like epic sword masters from the classic pulp adventure romances?

Thats the Swashbuckler class; stylish, witty and fucked against opponent's whose armour is made not of good humour but steel. Better off using the Daring multi-class feats with Rogue or Fighter and getting some decent feats or class features. Or house-ruling a Daring Weeaboo feat for Swordsage/Warblade synergy.

In 3rd edition this was a class in Complete Warrior. Since this was an early 3.5 book made when WotC hadn't yet acknowledged martials were stupidly underpowered (this was the book responsible for the Samurai class that's barely better than the Warrior NPC class), like most martial classes in 3.5 there was little reason to stay in it beyond a dip. The main way of making it work was to take 3 levels to get Insightful Strike (intelligence to damage) and Gish (this is still worse than one level dip gish due to less casting, but not terrible). Complete Scoundrel retroactively saved the Swashbuckler by adding the Daring Outlaw feat, which made Swashbuckler levels stack with Rogue levels for determining sneak attack damage while maintaining full BAB (minus 1). This didn't get as much popularity as the Ranger+Scout counterpart Swift Hunter because Swashbuckler was a worse class than Ranger and only Swift Hunter had a way to bypass immunity to Sneak Attack, but it did save the class from total pointlessness.

In Pathfinder, this class is basically a Gunslinger except he uses one-handed stabby weapons (especially rapiers) instead of firearms. He's a squishy fighter who has some MAD with Charisma (for panache points, the class's equivalent of gunslinger grit) and Dexterity and only gets light armor without spending feats. Worst of all, a Cavalier gets an archetype in the same book Swashbuckler was introduced in that gets all of a Swashbuckler's GOOD abilities and can do better, while Magus can cherry pick some of the better ones. Swashbuckler is perhaps the weakest martial PC class in Pathfinder: Even with feat investment its damage can't really compete with a great sword wielding Warrior whose only feat is power attack, while its AC takes too long to surpass heavy armor, and doesn't even get the wealth of quality archetypes the pre-Unchained Monk got. They can still throw out or block a lot of damage around with their panache/grit points, and they regenerate them fairly quickly and easily, but lots of other martial classes can do the same, and without the frills. Aside from being able to add their charisma modifier to a save a few times a day, they have no protection against spells. Even their official description can't really say they shine that much, saying they need to steal killing blows!

While different classes, both Swashbucklers are Tier 5 (though the Pathfinder version could fall into tier 6). They are also both there for the same reason: They focus on poor fighting styles without really doing anything to make them not suck, gain no meaningful class features after the first few levels, don't have enough skill points to be useful in that role, and have poor saving throws. They are useful exclusively as a dip, if that, only. If you want to play a movement based swashbuckling hero, play something from the Book of Nine Swords/Path of War, or at least Swift Hunter based Ranger/Scout or an Unchained Rogue with a Slayer dip.

5e brought back the Swashbuckler as a new Rogue archetype in Unearthed Arcana. They get to add their Charisma bonus to initiative, Sneak Attack enemies with none of the Swashbuckler's allies next to them, and don't provoke AoOs from enemies they attack in melee. And that's just at level 3. It got promoted to official with the Sword Coast Adventurers' Guide.

Or, if that's not Errol Flynn enough for you, you can take the College of Swords Bard, also from Unearthed Arcana, which takes its cues from the Blade bardic kit of Advanced Dungeons & Dragons. You get a bunch of fancy weapon tricks, extra attacks, and expertise in two-weapon fighting, plus the ability to spice your skills up with magic.

Dungeons & Dragons 3rd Edition Classes
Player's Handbook: Barbarian - Bard - Cleric - Druid - Fighter - Monk
Paladin - Ranger - Rogue - Sorcerer - Wizard
Player's Handbook II: Beguiler - Dragon Shaman - Duskblade - Knight
Complete Adventurer: Exemplar - Ninja - Scout - Spellthief
Complete Arcane: Warlock - Warmage - Wu jen
Complete Divine: Favored Soul - Shugenja - Spirit Shaman
Complete Psionic: Ardent - Divine Mind - Erudite - Lurk
Complete Warrior: Hexblade - Samurai - Swashbuckler
Dragon Compendium: Battle Dancer - Death Master - Jester
Mounteback - Savant - Sha'ir - Urban Druid
Dragon Magazine: Sha'ir - Deathwalker - Fleshcrafter - Soul Reaper
Dragon Magic: Dragonfire Adept
Dungeonscape: Factotum
Eberron Campaign Setting: Artificer
Heroes of Horror: Archivist - Dread Necromancer
Magic of Incarnum: Incarnate - Soulborn - Totemist
Miniatures Handbook: Favored Soul - Healer - Marshal - Warmage
Oriental Adventures: Samurai - Shaman - Shugenja - Sohei - Wu jen
Psionics Handbook: Psion - Psychic Warrior - Soulknife - Wilder
Tome of Battle: Crusader - Swordsage - Warblade
Tome of Magic: Binder - Shadowcaster - Truenamer
NPC Classes: Adept - Aristocrat - Commoner - Expert - Magewright - Warrior
Class-related things: Favored Class - Gestalt character - Multiclassing
Prestige classes - Variant Classes - Epic Levels
The Classes of Pathfinder
Core Classes: Barbarian - Bard - Cleric - Druid - Fighter - Monk
Paladin - Ranger - Rogue - Sorcerer - Wizard
Player's Guide:
Alchemist - Antipaladin - Cavalier
Inquisitor - Oracle - Summoner - Witch
Class Guide:
Arcanist - Bloodrager - Brawler - Hunter - Investigator
Shaman - Skald - Slayer - Swashbuckler - Warpriest
Kineticist - Medium - Mesmerist
Occultist - Psychic - Spiritualist
Ultimate X: Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante