Per quote garrysmod.org:
Allows you to control what weapons are available to you upon re-spawn. Also offers weapon dropping and ammo procurement.
dropweapon - Drops your active weapon.
giveprimaryammo - Gives 1 primary ammunition.
givesecondaryammo - Gives 1 secondary ammunition.
wep_spawnmode - Set this to change which weapons on spawn.
0: No Weapons
1: Garry’s Tools
2: Keep Weapons on Death
3: Default Weapons (Default)
If you want to use this on your server, feel free to remove the dropweapon.lua and giveammo.lua files.