From the back of the book
A Stat-Block for Every Occasion!
We've all been there: all of a sudden, you realize that you probably should have realized that your PCs would wind up charging the palace guard instead of talking it out with the vizier, and really wish you had stat-blocks for the fight. Or it occurs to you that, really, the wizard apprentice that they're rescuing from demon cultists should probably be trying to help in the fight, too, since his life is on the line, and everything. It's just that you don't know what his attack bonus is, and his level's a bit fuzzy, for that matter.
GM's Gallery: Useful and Interesting NPCs provides a total of 20 NPCs from CR 1 to 5, with stat-blocks that were designed to allow them to fill specific roles that GMs often find themselves needing, such as innkeeper, street urchin, brigand, town guard, and so on. Further, in order to keep things interesting, each stat-block has its own unique special ability, specifically designed for the role that NPC is supposed to fulfill. The whole package is rounded out with a brief tactics entry, which gives some suggestions not only for battle tactics, but also for roleplaying NPCs of that type.
If you're looking for some useful stat-blocks that are generic enough to be versatile but unique enough to retain some flavor, look no further than GM's Gallery: Useful and Interesting NPCs. After all, it's free!