Most played cards in The Rock:

5 Decks
Sudden Death
20 copies - 4 average
Damnation
20 copies - 4 average
Call of the Herd
18 copies - 3.6 average
Wall of Roots
16 copies - 3.2 average
Terramorphic Expanse
15 copies - 3 average
Spike Feeder
15 copies - 3 average
Mwonvuli Acid-Moss
15 copies - 3 average
Harmonize
15 copies - 3 average
Krosan Grip
13 copies - 2.6 average
Urza's Factory
11 copies - 2.2 average
Enslave
10 copies - 2 average
Weatherseed Totem
10 copies - 2 average
Twisted Abomination
10 copies - 2 average
Darkheart Sliver
10 copies - 2 average
9 copies - 1.8 average
Urborg, Tomb of Yawgmoth
9 copies - 1.8 average
Magus of the Library
8 copies - 1.6 average
Tendrils of Corruption
8 copies - 1.6 average
Search for Tomorrow
7 copies - 1.4 average
Augur of Skulls
4 copies - 0.8 average