open your console and type "sv_cheats 1"
open your console and type "mp_drop_knife_enable 1"
now copy&paste the commands from down below!

give weapon_knife_css;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_widowmaker;;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_gut;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_stiletto;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_gypsy_jackknife;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_ursus;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_falchion;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_survival_bowie;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_flip;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_push;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_tactical;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_m9_bayonet;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_bayonet;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_butterfly;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_karambit;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_cord;ent_fire weapon_knife addoutput "classname weapon_knifegg"

give weapon_knife_skeleton;ent_fire weapon_knife addoutput "classname weapon_knifegg"

- It spawned it in but i could not use it, any help?
Probably, you entered only this part of command - give weapon_knife_outdoor;
You have to add ent_fire weapon_knife addoutput "classname weapon_knifegg" to make dropped knife usable.
Also, do not forget to set mp_drop_knife_enable 1; to make available dropping knives.
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- can i be banned for this?
No, it works only on local servers, where sv_cheats allowed.
It is the same if you drop yourself AWP or another gun ( give weapon_awp / give weapon_ak47 ).
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- it doesnt work

If it doesnt work, be sure that you copied commands accurately.
If you copied commands without " symbol, it will drop, but you wont be able to get it.
So, do not forget ent_fire weapon_knife addoutput "classname weapon_knifegg" this part, thats necessary.
Do not forget to copy sv_cheats 1 and mp_drop_knife_enable 1.
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- does it work in real game?

Unfortunately, no. Only on servers with sv_cheats 1.
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- can i get like non vanilla like for example i want a karambit slaughter what do i type to spawn?

Unfortunately, no. You need to pay for skin ;(