Most played cards in Grixis Pyromancer:

2 Decks
Misty Rainforest
8 copies - 4 average
Force of Will
8 copies - 4 average
Gitaxian Probe
8 copies - 4 average
Cabal Therapy
8 copies - 4 average
Mental Misstep
8 copies - 4 average
Polluted Delta
6 copies - 3 average
Preordain
6 copies - 3 average
Volcanic Island
6 copies - 3 average
Gush
6 copies - 3 average
Grafdigger's Cage
6 copies - 3 average
Young Pyromancer
6 copies - 3 average
Baleful Strix
4 copies - 2 average
Smelt
4 copies - 2 average
Underground Sea
4 copies - 2 average
Surgical Extraction
4 copies - 2 average
Notion Thief
4 copies - 2 average
Dack Fayden
4 copies - 2 average
Sudden Shock
4 copies - 2 average
Flusterstorm
4 copies - 2 average
Pyroblast
4 copies - 2 average