The top picks not in lane to counter Fiddlesticks include Kalista, Samira, and Draven. These champions are all good at countering Fiddlesticks with decent win rates over 54%. Even if these Fiddlesticks counter picks are not taken opposite your position, it's not smart to play him into these matchups. They will usually crush Fiddlesticks.
Conversely, if the opposite team choses either Galio or Tahm Kench, Fiddlesticks mains should seriously consider taking him, as he easily destroys these champs with win rates over 55% against each ofthem.