As I was working on the various "inverted" classes, especially the Cavalier class, I thought "a Noble class would definitely fit this pattern." In fact, I was thinking of making noble houses as part of the elite orders. But then I decided that the Noble class should be reserved for the non-martial nobility, the people who don't want to fight in battle, but instead rely on mercenaries to fight their battles for them, or who wage wars of intrigue to defeat rivals. Members of the upper classes usually become either Nobles or Cavaliers, depending on their personality, but some opt for one of the common classes instead.
NobleConcept: The ruling class or idle rich. Arrogant, privileged, out of touch, possibly cynical or extremely naive.
Alignment: Any, but Chaos is uncommon, except among the corrupt nobility.
XP/HD: As Cleric, but the prime ability is Charisma with the same inverted experience bonus as Cavaliers (penalty for high Charisma, bonus for low Charisma.)
Weaponry and Armor: Any armor, but only skilled with weapons purchased when character is created. All other weapons are used at zero-level ability.
Limitations: Like Cavaliers, Nobles are horrified or frightened when confronted with a situation that violates their sense of the way things ought to be. This isn't always framed as "honor", but might instead be "propriety" or "respect". If confronted by a lower class opponent pretending to be a knight or noble, or if forced to do something they consider shameful or beneath their station, NPC Nobles make a morale check at -2, and PC Nobles must save vs. fear at -2 or be at Move 3/act last until the situation changes. Note that this isn't limited to combat, since Nobles may wind up in many "horrifying" non-combat situations, like having to stay at an inn that caters to peasants. GM should include at least two arbitrary conditions, such as "manual labor" or "not having enough servants" (at least one servant per level.) Players should pick one personal taboo that they consider beneath their station.
If a Noble is seen or rumored to behave in a low-class manner, make a reaction roll for social level drain. Other nobles react at -1 to "drained" PCs until their reputation is restored. Nobles are also at -1 reaction from peasants and others they treat as beneath them.
Abilities: All nobles can "speak with authority", which works like Turn Undead, but only on others of their own race and a lesser social rank. This allows them to bully citizens into leaving them alone, or to command that someone be captured or punished. Those ordered to obey aren't under mind control, they're just firghtened about what might happen if they disobey. In addition, each variety of noble has an additional power unique to their kind. For example, a Merchant Prince always knows the value of a mundane item and gets a +2 save if magic is used to mislead them in a trade. I'll have a follow-up detailing some other possible noble houses later...
Other: Triple starting wealth, just like the Tourist class. They may also have access to equipment prohibited for commoners, although probably not the crazy kinds of equipment available to Tourists.