Most played cards in 4C-Rack:

1 Decks
Lightning Bolt
4 copies - 4 average
Hymn to Tourach
4 copies - 4 average
Scrubland
4 copies - 4 average
Mishra's Factory
4 copies - 4 average
Hypnotic Specter
4 copies - 4 average
City of Brass
4 copies - 4 average
Sinkhole
3 copies - 3 average
The Rack
3 copies - 3 average
Order of the Ebon Hand
3 copies - 3 average
Ivory Tower
3 copies - 3 average
Red Elemental Blast
3 copies - 3 average
Su-Chi
3 copies - 3 average
Dark Ritual
3 copies - 3 average
Disenchant
3 copies - 3 average
Circle of Protection: Red
2 copies - 2 average
Swords to Plowshares
2 copies - 2 average
Maze of Ith
2 copies - 2 average
Badlands
2 copies - 2 average
Terror
2 copies - 2 average
Blue Elemental Blast
2 copies - 2 average