This addon replaces the following base game assets:
The crowbar hitsound
The shotgun reload sound
The shotgun pump sound
The crossbow fire sound

There may be more assets but I'm not sure at the moment, I'll look for the actual file names of the sounds at some point.

Note to developers:
Please remove these conflicts so if anyone else wants to see/hear the vanilla assets or has their own asset replacement they can use it without it getting overwritten with this mods assets.

EDIT:
I finally found time to look through all the files and I found all the conflicting assets, here they are:
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Identical files conflicting:
materials\models\weapons\v_357\357_sheet.vmt
materials\models\weapons\v_357\357_sheet.vmf
materials\particle\particle_ring_wave_10.vmt
materials\particle\particle_ring_wave_10.vtf
particles\grenade_fx.pcf
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So you may be asking yourself why it's replacing weapon sounds if there are no other conflicting files. It's because he's changing the sound scripts through Lua and some of the names of the already existing sound scripts he's overriding with the new Black Mesa sounds. These are the conflicting sound script entries:
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weapon_357.Reload
weapon_shotgun.Empty
weapon_shotgun.Reload
weapon_shotgun.Special1
weapon_crowbar.Melee_Hit
weapon_crossbow.Reload
weapon_crossbow.Single
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You also have a duplicate entry of "weapon_shotgun.Reload_NPC"
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Lastly you have a ton of garbage like VGUI ammo/medkit/battery pickup images and misc whatnot that aren't used, just remove that stuff like that please.
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I gave you the cheat sheet now please fix the damn addon.