It isn't really a cheat, but some mods will allow you to carry multiple weapons, like SuperHero Mod, or Zombie Mod. You can shift through them just like in HL.
There are no official cheats unless you are admin of the server.
sv_gravity_70
I don't think there is cheats. All I know is that you have to unlock levels to get new weapons.
Play legit.
random
Unknown but you can type up cheats for San Andreas on google etc and you will find cheats to get lots of weapons or some weapons.
I think there are no cheats aside from creating multiple accounts
Godmode
sensei all weapons
hgjhhj
yes
cheats for myriad island are same as cheats of vice city i.e thugstools for weapons set all cheats and their action are same