Why isn't the tool giving a hat?

Simple. You are calling Clone() function 6 times, so you'll get 6 hats. And every one is misconfigured.

for i, v in pairs(game.Workspace:GetChildren()) do
	if v:IsA("Hat") and v.Name == "Duh" then
		v:Clone().Parent = Char -- copies an hat and parents it to the player
		v:Clone().Handle.Position = Char.Head.Position -- copies an second hat and puts it on player, but no parent
		v:Clone().AttachmentForward = Vector3.new(-0, -0.197, -0.98) -- third hat
		v:Clone().AttachmentPos = Vector3.new(0, -0.35, 0) -- fourth hat
		v:Clone().AttachmentRight = Vector3.new(1, -0, 0) -- fifth hat
		v:Clone().AttachmentUp = Vector3.new(0, 0.98, -0.197) --sixth hat
	end
end

To solve this problem, we should use a variable, once Clone() function returns the copied object.

for i, v in pairs(game.Workspace:GetChildren()) do
	if v:IsA("Hat") and v.Name == "Duh" then
		local hat = v:Clone() -- copies the hat and returns it. Now, hat is the hat!
		hat.Parent = Char -- parents the copied hat
		hat.Handle.Position = Char.Head.Position -- puts it on player
		hat.AttachmentForward = Vector3.new(-0, -0.197, -0.98) -- stuff
		hat.AttachmentPos = Vector3.new(0, -0.35, 0) -- hat stuff
		hat.AttachmentRight = Vector3.new(1, -0, 0) -- more hat stuff
		hat.AttachmentUp = Vector3.new(0, 0.98, -0.197) --even more hat stuff
	end
end

Hope I helped! :)