Most played cards in Mardu:

3 Decks
Badlands
12 copies - 4 average
Disenchant
12 copies - 4 average
Sedge Troll
12 copies - 4 average
Hypnotic Specter
12 copies - 4 average
City of Brass
11 copies - 3.67 average
Scrubland
11 copies - 3.67 average
Lightning Bolt
11 copies - 3.67 average
Red Elemental Blast
10 copies - 3.33 average
Juzám Djinn
8 copies - 2.67 average
Swords to Plowshares
8 copies - 2.67 average
Hymn to Tourach
8 copies - 2.67 average
Fellwar Stone
6 copies - 2 average
Mishra's Factory
6 copies - 2 average
Underworld Dreams
5 copies - 1.67 average
Disrupting Scepter
4 copies - 1.33 average
Circle of Protection: Red
4 copies - 1.33 average
The Rack
4 copies - 1.33 average
Terror
4 copies - 1.33 average
Demonic Tutor
3 copies - 1 average
Armageddon
3 copies - 1 average