One instrument, many sounds
A guitar can be plucked or strummed, clean or distorted, acoustic or electric, nylon or steel. Free guitar samples cover single notes, full chords, harmonics, muted chugs and the small noises between notes that make a part sound human. Multisampled guitars from projects such as the Versilian Community Sample Library and other free libraries let you play a guitar from a keyboard.
Making samples sound played
Guitarists rarely hit every string at once, so stagger the notes of a chord by a few milliseconds, faster for a hard strum, slower for a gentle one. Alternate up and down strums with slightly different velocities. Most guitar samples have their root note in the title or on the card; tune them against your track before you map them.
For ready-made performances, see the guitar loops collection. For each sample here, the verdict says whether it can go in a release.