Parker's N'zoth

These are generally the cards you want to mulligan for unless you are facing a certain deck type such as zoolock, etc. Acidic swamp ooze can be great at slowing down Midrange Shaman's early game, using to kill spirit claws. Loot Hoarder gives this deck early board presence and card draw and Doomsayer is also great at slowing down aggressive decks. Acolyte is a good turn three used for drawing cards. Truesilver is great at controlling the board into the mid game. 

Barnes is a pretty aggressive pick in my opinion. The earlier you play it the less likely you could pull a larger minion in the late game. Aldor can also be a risky pick depending on whether your opponent is aggressive or more control oriented. 

Doomsayer is great for controlling the early game and Equality with Pyromancer is a fantastic board clear. Usually I keep Equality or Pyro/Consecration if I'm facing a very aggressive deck such as zoolock.