Most played cards in Discard:

2 Decks
Bad Moon
4 copies - 2 average
Hymn to Tourach
4 copies - 2 average
The Rack
4 copies - 2 average
Hypnotic Specter
4 copies - 2 average
Sinkhole
4 copies - 2 average
Dark Ritual
4 copies - 2 average
Order of the Ebon Hand
4 copies - 2 average
Royal Assassin
3 copies - 1.5 average
Cuombajj Witches
3 copies - 1.5 average
Gloom
3 copies - 1.5 average
Terror
3 copies - 1.5 average
Black Knight
3 copies - 1.5 average
Drain Life
2 copies - 1 average
Sengir Vampire
2 copies - 1 average
Mishra's Factory
2 copies - 1 average
Disrupting Scepter
2 copies - 1 average
Howl from Beyond
1 copies - 0.5 average
Mind Twist
1 copies - 0.5 average
Strip Mine
1 copies - 0.5 average