I've been looking at Output's Signal and Exhale lately, and was wondering what other non-Native Instruments released libraries other producers have found to be hidden gems or really useful additions to their Kontakt Libraries. Any thoughts?

Anything by 8dio is typically awesome. Some good Cinesamples stuff out there as well.

8Dio + ProjectSAM

- Spitfire Audio for some great orchestral samples, especially the Albion Series but they also got all sort of other libraries (e.g. Spitfire Labs = Donationware)
- Atom Hub makes some cheap libraries based around all kind of sounds found in a particular environment (e.g. Bathroom, Park, Cellar). Very cool for some little household percussions most of the time.
- Embertone makes really high quality libraries of solo instruments for quite cheap