Autodafe has released Acoustic Bass, a free acoustic bass instrument library for Native Instruments Kontakt.
I have released a set of samples of an Acoustic Bass, an old Ibanez sampled years ago.
Custom scripted in Kontakt 5.3 (need the full edition to play, not the player).
There are three presets: a fingered bass, a muted bass an a picked bass.
The Acoustic Bass library is a free download.