The greatest picks out of lane to counter Shaco include Lucian, Kalista, and Aphelios. These are all good at countering Shaco with decent win rates over 55%. Even if these Shaco counter picks are not chosen opposite your position, it's not smart to take him into any of these matchups. They will very likely destroy Shaco.
Conversely, if the other team picks either Karthus or Shyvana, Shaco mains should seriously think about picking him, as he easily crushes these champions with win rates over 53% against each ofthem.