Most played cards in Thassa, God of the Sea:

3 Decks
Pithing Needle
3 copies - 1 average
Orbs of Warding
3 copies - 1 average
Sapphire Medallion
3 copies - 1 average
Oblivion Stone
3 copies - 1 average
Sorcerous Spyglass
3 copies - 1 average
Omniscience
3 copies - 1 average
Vedalken Shackles
3 copies - 1 average
Thaumatic Compass
3 copies - 1 average
Forcefield
3 copies - 1 average
Whir of Invention
3 copies - 1 average
Pact of Negation
3 copies - 1 average
Opt
3 copies - 1 average
Negate
3 copies - 1 average
Psionic Blast
3 copies - 1 average
Remand
3 copies - 1 average
Turnabout
3 copies - 1 average
Reweave
3 copies - 1 average
Academy Ruins
3 copies - 1 average
Arch of Orazca
3 copies - 1 average
Rishadan Port
3 copies - 1 average