Most played cards in 8-Cast:

4 Decks
Lotus Petal
16 copies - 4 average
Force of Will
16 copies - 4 average
Mishra's Bauble
16 copies - 4 average
Ancient Tomb
16 copies - 4 average
Urza's Bauble
16 copies - 4 average
Thoughtcast
16 copies - 4 average
Chalice of the Void
16 copies - 4 average
Mox Opal
16 copies - 4 average
Urza's Saga
16 copies - 4 average
Seat of the Synod
16 copies - 4 average
Thought Monitor
15 copies - 3.75 average
Emry, Lurker of the Loch
15 copies - 3.75 average
Force of Negation
14 copies - 3.5 average
Sai, Master Thopterist
13 copies - 3.25 average
Dismember
11 copies - 2.75 average
Kappa Cannoneer
11 copies - 2.75 average
Otawara, Soaring City
8 copies - 2 average
Brazen Borrower
7 copies - 1.75 average
Flusterstorm
6 copies - 1.5 average
Tormod's Crypt
5 copies - 1.25 average