How would I use LocalPlayer in a server script?

This is what I have in the classic paintball gun, from line 29 in 'Paintball'

	if humanoid ~= nil or localplayer then
		tagHumanoid(humanoid)
		humanoid:TakeDamage(damage)
		wait(1)
		untagHumanoid(humanoid)
	end

The entire script:

ball = script.Parent
damage = 50

function onTouched(hit)
	local humanoid = hit.Parent:FindFirstChild("Humanoid")
	if hit:getMass() < .5 * 200 then
		hit.BrickColor = ball.BrickColor
	end
for i=1, 1 do
	local s = Instance.new("Part")
	s.Shape = 1 
	s.formFactor = 2 
	s.Size = Vector3.new(1,.4,1)
	s.BrickColor = ball.BrickColor
	local v = Vector3.new(math.random9(-1,1), math.random(0,1), math.random(1,1))
	s.Velocity = 15 * v
	s.CFrame = CFrame.new(ball.Position + v, v)
	ball.BrickCleanup:clone().Parent = s
	s.BrickCleanup.Disabled = false
	s.Parent = game.Workspace	
end

if humanoid ~= nil then
	 tagHumanoid(humanoid)
		humanoid:TakeDamage(damage)
		wait(1)
		untagHumanoid(humanoid)
end

connection:Disconnect()
ball.Parent = nil
end

function tagHumanoid(humanoid)
	local tag = ball:FindFirstChild("creator")
	if tag ~= nil then
		local new_tag = tag.clone()
	end
end

function untagHumanoid(humanoid)
	if humanoid ~= nil then
		local tag = humanoid:FindFirstChild("humanoid")
		if tag ~= nil then
			tag.Parent = nil
		end
	end
end

connection = ball.Touched:connect(onTouched)
wait(3)
ball.Parent = nil

The server has no 'Local Player'. It's only achievable inside a local script because local scripts run on the clients' computer, rather than a server script, which only runs on the server and has no relations with any of the clients therefore local player doesn't exist on the server.

However, there are other ways of getting the player on the server, if you're using events such as a Touched event which returns the part that came into contact with the given part, you can then find the player by using the Players:GetPlayerFromCharacter() function and include the parent of the part that was returned. If it was a character's body part that was returned, then the parent of that part would be the character.

Please accept answers so we know if you've found help.

@xInfinityBear provided you an excellent answer.