Best quests were (can't put them in any order...): Ladies Of The Woods (that stunning moment when real Ladies appear), Possession (maybe the best WTF moment in the game), Greedy God, Dead man's Party (just hilarious and crazy) and Without A Trace (they fooled me completely with this nicely done quest).
Oh! And a Tome Entombed(?) (that vampire in the coffin in the sewers)
All Gwent quests.