Binding 'taken' keys?

I recommend looking into UserInputService events. They are harder to understand than regular mouse events, but it will let you use any key on keyboard as well as some other fancy inputs.

So to bind the '/' key, you could use this script:

inputService = game:GetService("UserInputService")

inputService.InputBegan:connect(function(input)
	if input.UserInputType == Enum.UserInputType.Keyboard then
		if input.KeyCode == Enum.KeyCode.Slash then
			print("/ key has been pressed!")
		end
	end
end)