Most played cards in U/R Eldrazi:

1 Decks
Hedron Archive
4 copies - 4 average
Wandering Fumarole
4 copies - 4 average
Anticipate
4 copies - 4 average
Clash of Wills
4 copies - 4 average
Spell Shrivel
4 copies - 4 average
Spatial Contortion
4 copies - 4 average
Shrine of the Forsaken Gods
4 copies - 4 average
Shivan Reef
4 copies - 4 average
Mage-Ring Network
4 copies - 4 average
Highland Lake
4 copies - 4 average
Ulamog, the Ceaseless Hunger
3 copies - 3 average
Kozilek's Return
3 copies - 3 average
Fiery Impulse
3 copies - 3 average
Reality Smasher
3 copies - 3 average
Negate
3 copies - 3 average
Drowner of Hope
3 copies - 3 average
Fevered Visions
2 copies - 2 average
Thought-Knot Seer
2 copies - 2 average
Spawning Bed
2 copies - 2 average
Chandra, Flamecaller
2 copies - 2 average