Near the end of last year there was a Kickstarter for the creation of a 100% no strings attached sound effects library for firearms. It was successfully funded, and has been released under a CC0 license - no royalties, no credit required.
They have now started another Kickstarter for a medieval sound effects library, if you care to donate. (https://www.kickstarter.com/projects/bjjaszcz/the-medieval-weapons-sound-effects-library)
(edit: fixed url tag ~neo)