Most played cards in Sliver Queen:

4 Decks
Breeding Pool
5 copies - 1.25 average
City of Brass
4 copies - 1 average
Command Tower
4 copies - 1 average
Sylvan Library
4 copies - 1 average
Swords to Plowshares
4 copies - 1 average
Demonic Tutor
4 copies - 1 average
Mana Confluence
3 copies - 0.75 average
Hallowed Fountain
3 copies - 0.75 average
Jace, the Mind Sculptor
3 copies - 0.75 average
Watery Grave
3 copies - 0.75 average
Fact or Fiction
3 copies - 0.75 average
Toxic Deluge
3 copies - 0.75 average
Underground Sea
3 copies - 0.75 average
Polluted Delta
3 copies - 0.75 average
Windswept Heath
3 copies - 0.75 average
Flooded Strand
3 copies - 0.75 average
Reflecting Pool
3 copies - 0.75 average
Temple Garden
3 copies - 0.75 average
Overgrown Tomb
3 copies - 0.75 average
Bayou
3 copies - 0.75 average