Came across this link today while looking for a shotgun sound:
(haven't seen it here yet)

Quote:

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Each sound effect is royalty-free and can be used for both commercial and personal use. (mp3 and wav)

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http://www.flasherdot.org/4_SE.htm

[EDIT]
Here's one more:
http://www.therecordist.com/pages/game_sfx.html