My attempt at fixing the mounting issues GMod has with Team Fortress 2. You should disable/unsubscribe from any other TF2 mounting fixes before subscribing to this.
This dynamically replaces the conflicting textures when you load a Team Fortress 2 map, meaning you won't have to deal with disabling the addon on HL2 maps and re-enabling it on TF2 maps. It also includes fixes for the particle mounting, a small fix for maps that used voice lines from before TF2 changed them to .mp3 files, and a fix for the TF2 shotgun using the textures if the HL2 shotgun.
Note: If you're on a TF2 map and the texture fix doesn't automatically apply for some reason, use the console command "tf_applyfixup" This can also be used on non-TF2 maps, though it isn't recommended