Most played cards in All Spells:

2 Decks
Pact of Negation
8 copies - 4 average
Echoing Truth
8 copies - 4 average
Sea Gate Restoration
8 copies - 4 average
Balustrade Spy
8 copies - 4 average
Chrome Mox
8 copies - 4 average
Dark Ritual
8 copies - 4 average
Force of Will
8 copies - 4 average
Agadeem's Awakening
8 copies - 4 average
Narcomoeba
8 copies - 4 average
Leyline of the Void
8 copies - 4 average
Undercity Informer
8 copies - 4 average
Slaughter Pact
6 copies - 3 average
Goblin Charbelcher
6 copies - 3 average
Cabal Therapy
3 copies - 1.5 average
Mox Pearl
2 copies - 1 average
Mox Jet
2 copies - 1 average
Hurkyl's Recall
2 copies - 1 average
Mox Emerald
2 copies - 1 average
Mox Ruby
2 copies - 1 average
Blightsteel Colossus
2 copies - 1 average