Free for Kontakt
 
Karoryfer has released two free open-source sample libraries:Emilyguitar and Growlybass.
Emilyguitar features:

• Samples of an Epiphone Emily the Strange guitar with flatwound strings.
• A total of 323 24-bit 44.1 kHz WAV samples.
• Notes sampled every minor third.
• Four velocity layers and three round robins.
• String release noises with four round robins.
• Various percussive and fingering noises with five round robins.
• Six different SFZ mappings - four for single notes and two for chords.
• 98 MB download size.

Growlybass features::

• Samples of a Squier Jazz bass guitar with roundwound strings.
• A total of 310 24-bit 44.1 kHz WAV samples.
• Notes sampled every minor third.
• Sustained notes with four velocity layers and four round robins.
• Staccato notes and string release noises with one velocity layer and five round robins.
• Pick scrapes with four round robins.
• Seven different SFZ mappings.
• 159 MB download size.

Price: Free.

That bass sounds like it's worth a look. It would be a lighter load than my other sampled basses, some of which are crazy huge. I often fall back to SI-Bass or SampleTank 2.5 just because they're so lightweight. My all-time favorite bass library (OTS Rick) is so huge I sometimes can't use it.
 
But be aware that there is no Kontakt instrument definition for it, so if you want to use it in Kontakt you'll have to make your own mapping. Fortunately, with "only" 310 samples that'd do-able. There are SFZ mappings, though.