I was wondering how I would go about doing this (Take Before the dawn for an example, When your the slasher, you have an auto equipped weapon and it doesn't appear in your inventory but you can still use it) also, how would I go about making it so it does something when you click (say a knife and once clicked it stabs (Just wondering how you'd make the click as well))
To keep the inventory empty, maybe disable the CoreGUI for the toolbar using a localscript in startercharacterscripts so nobody can view their inventory or interact with it.
game:GetService('StarterGui'):SetCoreGuiEnabled(Enum.CoreGuiType.Backpack, false)
Then, you could use the knife as a tool and just use the function EquipTool().
game.Players.LocalPlayer.Humanoid:EquipTool(game.StarterPack.knifarino)
For the onClick, here's a place with all the scripts and explanations that are better than mine. http://wiki.roblox.com/index.php?title=Tools
Just drag the tool into StarterPack
about the click thing try:
local function onClicked() --ur script end script.Parent.MouseButton1Click:connect(onClicked)
edit: you also need animations so watch this vid: https://www.youtube.com/watch?v=ugJAzcjmS4Q