Most played cards in Madness:

3 Decks
Wild Mongrel
12 copies - 4 average
Basking Rootwalla
12 copies - 4 average
Circular Logic
8 copies - 2.67 average
Windswept Heath
8 copies - 2.67 average
Aquamoeba
8 copies - 2.67 average
Careful Study
8 copies - 2.67 average
Arrogant Wurm
8 copies - 2.67 average
Deep Analysis
6 copies - 2 average
Chrome Mox
5 copies - 1.67 average
Yavimaya Coast
5 copies - 1.67 average
Wonder
5 copies - 1.67 average
Meddling Mage
4 copies - 1.33 average
Life from the Loam
4 copies - 1.33 average
Pithing Needle
4 copies - 1.33 average
Flooded Strand
4 copies - 1.33 average
Tranquil Thicket
4 copies - 1.33 average
Zombie Infestation
4 copies - 1.33 average
Putrefy
4 copies - 1.33 average
Cabal Therapy
4 copies - 1.33 average
Barren Moor
4 copies - 1.33 average