The Social Expert

The Social Expert is a character with people skills, especially when dealing with large groups of people. He can recognize the social patterns in a group, figure out people's motivations, and know who the person in charge is. The Social Expert can identify who's manipulatable, who's a manipulator, and who's neither. The Social Expert can make himself likable even to his enemies, and is normally clever enough not to make very many of them.

Social expertise is an alignment-neutral skill, but it's practically a prerequisite for Manipulative Bastard, Magnificent Bastard and The Chessmaster. Nearly every Deadly Decadent Court will have at least one, probably more. May also be The Charmer. Subtrope of The Face.

Protagonist Social Experts are Guile Heroes, supporting Social Experts end up as Mister Exposition, and villainous ones are normally large-scale Manipulative Bastards.

Anime

 * , the Big Bad of Bleach possesses this skill, when he bothers to use it.
 * Johan Liebert from Monster.
 * Light Yagami from Death Note.
 * Izaya Orihara from Durarara!!, aside from being a complete Troll and Manipulative Bastard and claiming to "love humanity" (except for Shizuo), also performs his own social experiments, such as encouraging depressed people contemplating suicide to do so, or making suicide pacts with them and then revealing he was just kidding and thinks they are idiots, just to see if they really will commit suicide or not. Or paying people to kidnapping someone, and then paying someone else to rescue them, just to see how they'll react. Yes, Izaya is a dick.
 * Both Lelouch Lamperouge and his older brother, Prince Schneizel, in Code Geass.

Literature

 * Mari in Salamander is a heroic version, serving as a Hypercompetent Sidekick in the world of politics to the Teen Genius Science Hero, Ellen.
 * Mister Wednesday from American Gods.
 * Cordelia Vorkosigan is the best example from the Vorkosigan Saga.
 * Vetinari and Moist von Lipwig from the Discworld books.
 * Jacky Faber of Bloody Jack learned the skills she needed to become one, mostly because she had to for the sake of survival.
 * A Song of Ice and Fire has quite a few, as would be expected given the high number of Manipulative Bastard and Chessmaster characters. Tyrion Lannister is a rare example of being this trope despite most people not actually finding him all that charming or likeable, partly because they assume Beauty Equals Goodness and he's an ugly dwarf, and partly because his Deadpan Snarker tendencies tend to irritate people.
 * Dumbledore, to such an extent that by the time you realize the full breadth of his planning and manipulation in book seven, he starts to look like a full-on Anti-Hero Magnificent Bastard.

Live-Action TV

 * The title character from The Mentalist.
 * Littlefinger from Game of Thrones. In one monologue which no one will likely remember, he explains how this is his only way of getting back at the other nobles.
 * Grifter Sophie Deveraux (or whatever her real name is) from Leverage. Her role on the team is to manipulate the mark with multiple "roles" that she plays, but often someone else needs to be sent in for one reason or another, and she'll coach them by reading the players and describing what she does and why.

Tabletop Games

 * Shadowrun. At least one character in the PC group needs to have good social skills to deal with the various NPCs the group will encounter. They should have high Charisma, good Etiquette skills and possibly cyberware/bioware that enhances those qualities (e.g. tailored pheromones). Such a person may be called "The Face" of the group.
 * Exalted has a threefold division between social skills, mental skills, and physical skills. Any character with high social skills is a social expert. Among the Solars, members of the Zenith and Eclipse castes have the greatest talent in this area.

Theater

 * Tranio in The Taming of the Shrew could be seen as this. Not only does he blend in perfectly with the group of rich guys who hang around Baptista's house (despite being a servant in disguise), he seems to have a handle on all their schemes as well as his own.

Video Games

 * from Jade Empire.

Web Original

 * Grandmaster of Theft's Cassidy Cain uses social grace as both herself and to assist as a Classy Cat Burglar.

Web Comics

 * Terezi in Homestuck is the most talented manipulator of the series thanks to being the Social Expert, contrasted with Vriska who relies on more direct Psychic Powers.
 * Elan in Order of the Stick is a story-telling expert because his role is the party bard. This makes him able to predict the actions and motivations of almost everyone involved.

Western Animation

 * Both Azula and Long Feng in Avatar: The Last Airbender.
 * Trent Lane in Daria, despite a personality so laid back that his communiques are seldom and brief, is often able to identify moments of mounting tension between his sister Jane and her titular best friend. A few times throughout the series he tries to drop subtle (well, slightly subtle) hints that steer the girls towards peaceful resolution.