Well, so far, out of everything published and released for my
Kaidan: a Japanese Ghost Story setting, there have been no PrC designs up until now.
There is one coming out with our
Way of the Yakuza - faction book, called a
'Machi-Yakko', which basically describes a yakuza street boss. I figured an archetype wouldn't work, as a fist level street boss makes no sense. By 6th level, an up-in-coming yakuza member could be elected to such a position if an opening is available. I think this fits theme, rather than niche.
The prerequesite classes for Machi Yakko are any of the allowed classes which are in the Yakuza, including: Moso (a blind bard), yakuza bushi (fighter), rogue bakuto (gambler), rogue kyodai (yakuza brother), and Horimyo (tattoo wizard) - along with skill minimum requirements.
The Machi Yakko gains some Sneak Attack progression, gains bonuses to Diplomacy, Leadership and Intimidation, gets a cut of gang profits, and 5 enchanted tattoos (which normally fill body slots, these tattoos for machi yakko do not.)
As stated, I haven't created any other Prestige Classes, but this one fills a particular theme in the yakuza.
I may or may not create more PrC - it all depends on needs for the setting.
GP