Remember that one kickass fencing scene from The Princess Bride where Wesley and Indigo 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 two 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. Without optimization a Swashbuckler can have less AC and damage than a warrior (the NPC class) in heavy armor swinging a two handed weapon.
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.
|The Classes of Pathfinder|
|Core Classes:|| Barbarian - Bard - Cleric - Druid - Fighter - Monk |
Paladin - Ranger - Rogue - Sorcerer - Wizard
| Arcanist - Bloodrager - Brawler - Hunter - Investigator |
Shaman - Skald - Slayer - Swashbuckler - Warpriest
| Alchemist - Antipaladin - Cavalier |
Inquisitor - Oracle - Summoner - Witch
| Kineticist - Medium - Mesmerist |
Occultist - Psychic - Spiritualist
|Ultimate X:||Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante|
| Aegis - Cryptic - Dread - Marksman - Psion |
Psychic Warrior - Soulknife - Tactician - Vitalist - Wilder
|Path of War:||Harbinger - Mystic - Stalker - Warder - Warlord - Zealot|