How can i make it so the function only gets triggered once every .5 seconds even if spamclicking?

Use the debounce method:

wait()
local player = game.Players.LocalPlayer
local tool = script.Parent

local CanClick = true -- debounce bool, this will determine if the function can fire (true) or not (false).

tool.Equipped:Connect(function(Mouse)


    Mouse.Button1Down:Connect(function()

	if CanClick then -- same thing as: 'if CanClick == true'
		CanClick = false -- set the debounce to false to prevent the function from firing
	    local ev = workspace.Events.PunchE
	
	    ev:FireServer()

		--COOLDOWN--
		wait(.5)
		CanClick = true
	end


    end)

end)