Attempt to index a nil value. What's wrong?

Okay, just to iron out a few potential problems, im going to tell the script to halt until the remote events and such exist.

--//Services

local replicatedStorage = game:GetService("ReplicatedStorage")

--//instances

local remoteEvents = replicatedStorage:WaitForChild("RemoteEvents") 
local killerTrapRemote = remoteEvents:WaitForChild("KillerTrap")

--//Functions

local function giveModel(player, partFolder, green)
if player and parFolder then
		local newPart = script:WaitForChild("StickModel"):Clone()
		newPart.Name = player.Name.."'s Trap"
		newPart.CFrame = player.Character:FindFirstChild("HumanoidRootPart").CFrame
		newPart.Parent = workspace
		wait(3)
		newPart.Code.Disabled = false
	end
end

--//Connections

killerTrapRemote.OnServerEvent:Connect(giveModel)

in your script, you werent accessing the player's character for the HumanoidRootPart, so I think that was the initial problem. To prevent any further issues, I added some functions that will make the script halt until they appear, so that you can avoid future errors similar to this.

When you use :FindFirstChild("HumanoidRootPart") on the player, it returns nil, because the player doesnt have a child called HumanoidRootPart. The character does, however.