Most played cards in Mardu:

2 Decks
Disenchant
8 copies - 4 average
Badlands
8 copies - 4 average
Swords to Plowshares
8 copies - 4 average
Scrubland
8 copies - 4 average
Juzám Djinn
8 copies - 4 average
Hypnotic Specter
8 copies - 4 average
Sedge Troll
8 copies - 4 average
City of Brass
7 copies - 3.5 average
Red Elemental Blast
7 copies - 3.5 average
Lightning Bolt
7 copies - 3.5 average
Fellwar Stone
6 copies - 3 average
Underworld Dreams
5 copies - 2.5 average
Hymn to Tourach
4 copies - 2 average
Terror
3 copies - 1.5 average
Armageddon
3 copies - 1.5 average
Sinkhole
2 copies - 1 average
Sol Ring
2 copies - 1 average
Fireball
2 copies - 1 average
Strip Mine
2 copies - 1 average
Demonic Tutor
2 copies - 1 average