NPC class PRCs?

[deuxhero]

(for the purpose "NPC Class" include the Gleaner over on the left, even though it is technically homebrew)

I know Survivor (commoner) is a big one, Hexer has requirements that really only Adept can hit normally (Lightning Bolt as a divine spell) and that one "aristocrat friendly prestige class that grants the extra ordinary ability to foll magical lie detection" (Spymaster).

I know a high level warrior could get into Blackguard and such and Chameleon was purposefully easy to enter, but are there any others that are
1. easier to enter via an NPC class than a PC class
2. Only possible with an NPC class
3. Abilitys that work well on NPCs
4. Have major increases in power from an NPC class.

[Nate the Snake]

1. easier to enter via an NPC class than a PC class

I think Survivor is the only one with that distinction. The Expert can get into anything that requires only skill ranks, but so can the Factotum.

2. Only possible with an NPC class

I think Hexer is the only one with that distinction. An Archivist could learn lightning bolt as a divine spell, but that would still require the Adept class to give access to the spell in the first place. (There's also the Generic Spellcaster, but that doesn't really count.)

3. Abilitys that work well on NPCs

Dungeonscape has the Dungeon Lord, an NPC prestige class. This sort of goes back to #1 and #2, since it's intended for NPCs, but PCs could technically qualify.

4. Have major increases in power from an NPC class.

We're talking about NPC classes, which are intentionally weak and have no class features, so very little wouldn't be an increase in power.

Along this line, there was a thread a while back about optimizing low tier classes, including NPC classes.

[vanyell]

the draconimicon (sp) PrCs. with wonderful prerequisites such as BAB +30 and true dragon, they were made solely for dragon NPCs

[Gnaeus]

Dwarf Defender has a range of abilities pretty much only useful to NPCs.

Libris Mortis is another book with a lot of good NPC classes (for undead progression).

[Zeta Kai]

The Dungeon Lord in Dungeonscape is explicitly designed for NPCs (specifically the BBEG variety).

Also, I've always looked at the Blackguard as an NPC class. I've never played a game that took a paladin down a path even close to Blackguard-iness.