Two different libraries of my double bass (the new one is warmer and more consistent, has extra samples of notes tuned all the way down to A, but the old one has more extreme velocities and some bow scratching noises). Also a cello, an electric upright, a few bass guitars and bagpipes. The electric upright goes down to E an octave below standard and could probably be processed into all kinds of massive drones.http://www.karoryfer.com/karoryfer-samples
96-301 MB and a couple hundred samples each, so not pro level but pretty good for freebies.
And I'm also completely serious about doing a library of death metal vocal phonemes. Should be done soon, but we want to add some complete pre-drop samples to it. Because your festival trap track needs a sample of a girl growling "all I wanna do is zooma zoom zoom zoom and a boom boom", or at least "the humans are coming".