Curse of the Crimson Throne
Alchemist, Arcanist, Magus, Sorcerer, Summoner, Witch, Wizard: Korvosa is welcoming to those who specialize in arcane magic, and there are numerous opportunities for an arcane spellcaster to flourish in the city—and being an adventurer is certainly one option for prosperity! One important thing to keep in mind, though, is that Korvosa's most well-known school for arcane spellcasters, the Acadamae, does not play a significant role in Curse of the Crimson Throne. If you wish your character to be associated with the Acadamae, speak to your GM or build your character so those links are relatively minor. All of the standard familiars are good choices in Korvosa. There is a long-standing feud in the city between imps (who've escaped servitude to Acadamae students and teachers) and pseudodragon-like creatures called house drakes. Both of these are classic choices for improved familiars. (A spellcaster must be 7th level and chaotic good to gain a house drake as a familiar; full statistics for these tiny dragons appear in Curse of the Crimson Throne.) Other commonly seen improved familiars in Korvosa include dire rats, lyrakien, nosois, and pseudodragons, but anything approved by your GM could serve.
Barbarian, Bloodrager, Druid, Hunter, Shaman, Skald: These classes are not normally associated with urban regions, but as long as you have a reason for your character to live in or be on an extended visit to Korvosa, the campaign will accommodate such characters (and in fact, when the plot moves beyond the city walls, such characters may well be particularly helpful!). A character associated with one of the Shoanti quahs might provide some additional advantages or opportunities as the campaign progresses, particularly if the PC hails from one of the quahs that dwells in the Cinderlands (the Lyrune-Quah, the Sklar-Quah, or the Skoan-Quah)—although if your PC is a member of one such tribe, don't assume that you'll be automatically welcomed back into your tribe's arms after spending a significant amount of time in Korvosa! Classes that take animal companions should be able to function normally in Korvosa—after all, this is a city where defenders mounted on hippogriffs exist. The sight of someone with an exotic animal companion is unlikely to raise many eyebrows, provided the animal companion is well behaved. Nonetheless, there are certain types of animal companions that are more commonly encountered in this part of Varisia, including alligators, badgers, bears, birds, boars, dogs, horses, ponies, small cats (mostly firepelt cougars), wolverines, and wolves.
Bard, Investigator, Rogue, Slayer, Swashbuckler: These intrigue-focused characters make excellent choices for an urban campaign like Curse of the Crimson Throne. Korvosa has a wide range of organizations and groups that characters like this can belong to, but the campaign works best for "freelancers"—intrigue-based characters who haven't yet selected a group to associate with, be they underground guilds or high society. As the Curse of the Crimson Throne campaign progresses, you'll encounter several groups with which your intrigue-themed character might ally with or oppose, and coming to these groups without having a strong affiliation at the outset makes for a more rewarding play experience. Of course, there's one group your intrigue-focused character should start quite loyal to—that of the player character party! If you want to associate with a particular group, speak to your GM before the game begins. Note also that any of these intrigue-focused characters could benefit from the specific information provided below for vigilante characters.
Brawler, Cavalier, Fighter, Monk: As with intrigue-focused characters, there are numerous options for martial classes to flourish in Korvosa. The most appropriate group to ally with in this campaign would be the Korvosan Guard, which serves as the city's police force and plays a significant role in the campaign. Other groups, like the Hellknight Order of the Nail and the Sable Company have specific roles to play in Curse of the Crimson Throne that make them poor choices for PCs. If you wish to associate with one of these two groups, speak with your GM before the game.
Cleric, Inquisitor, Oracle, Warpriest: All four of these divine spellcasting classes are well known and welcome in Korvosa—provided they do not use their religious beliefs and zeal to cause trouble. Consult the Religions section below for further details.
Kineticist, Medium, Mesmerist, Occultist, Psychic, Spiritualist: There are a few opportunities for psychic classes to particularly shine throughout the Curse of the Crimson Throne Adventure Path, be they links to the deep themes of spiritualism associated with the Harrow or explorations of particularly notorious haunted sites. Make sure your GM is familiar with and comfortable with options from Pathfinder RPG Occult Adventures before choosing one of these classes for your character.
Paladin: Paladins are an excellent choice for Curse of the Crimson Throne—with one caveat: do not let the lawful portion of your alignment rule your play choices. Things rapidly get out of control and go bad in Korvosa as the campaign unfolds, and your paladin's choices should put her or him firmly on the side of the PCs. Speak to your GM before playing a paladin in this game. As a general rule, it's probably better to play a paladin of a neutral good deity than of a lawful neutral deity in Curse of the Crimson Throne.
Ranger: If you choose to play a ranger, make sure to consult the information above for other nature-themed classes (barbarian, druid, etc.), including advice on animal companions. Note also that while Korvosa has a ranger-themed organization that operates within its walls (the Sable Company), that group is not a great choice for association with as a player character. If you wish to be associated with the Sable Company, clear it with your GM before play. The best options for favored enemy are animal, humanoid (human), undead, and vermin. These choices remain strong in the later parts of the campaign, but outsider (evil) and outsider (native) grow stronger as options. Most other favored enemy choices will be represented now and then in the campaign, but not nearly as often. The best favored terrain choices are (in descending order of importance) urban, underground, desert, swamp, and plains.
Gunslinger, Ninja, Samurai: These three classes are all but unknown in Korvosa. While samurai and gunslingers can fit in well with other martial-focused classes and ninja fit in well with intrigue-focused classes, there are no specific themes in Korvosa tailored specifically for these exotic class choices.
Vigilante: Korvosa's current political climate is ripe for the attention of a vigilante. In fact, the city already has one notorious legend in this category: Blackjack, a figure at once beloved and reviled, is a masked hero who has fought for Korvosa's downtrodden for many decades. Rumors about his or her identity, race, and gender are across the board, as are opinions as to whether Blackjack is one person or a role held by several over the course of the city's growth. Whatever the truth, Blackjack has been lying low of late, perhaps retired, perhaps dead, or perhaps (as the downtrodden hope) merely waiting for the right time to burst back onto the scene. Of course, this means the city is potentially ready for a new vigilante to look up to or to fight against. Your vigilante could even be interested in taking on the role of Blackjack, although if you do so, speak to your GM first to determine how that might be worked out.
Prestige Classes: The Harrow plays a significant role in Curse of the Crimson Throne, and as such, the harrower prestige class from Pathfinder Campaign Setting: The Inner Sea World Guide would make a particularly interesting choice for anyone who can qualify for it. Certain prestige classes are associated with key organizations in Golarion, and some of those organizations have key roles to play in Curse of the Crimson Throne. As such, these prestige classes are inappropriate for use in this campaign, but in order to avoid spoiling too much, those classes are not called out here. If you wish to build your character toward a specific prestige class, make sure to let your GM know as soon as possible so that she or he can either approve or deny your choice based on whether it makes sense to take levels in that class for Curse of the Crimson Throne.