Most played cards in Mardu Pyromancer:

2 Decks
Lingering Souls
8 copies - 4 average
Bloodstained Mire
8 copies - 4 average
Blackcleave Cliffs
8 copies - 4 average
Lightning Bolt
8 copies - 4 average
Bedlam Reveler
8 copies - 4 average
Young Pyromancer
8 copies - 4 average
Faithless Looting
8 copies - 4 average
Collective Brutality
8 copies - 4 average
Marsh Flats
7 copies - 3.5 average
Thoughtseize
7 copies - 3.5 average
Inquisition of Kozilek
7 copies - 3.5 average
Kolaghan's Command
6 copies - 3 average
Fatal Push
6 copies - 3 average
Blood Crypt
4 copies - 2 average
Blood Moon
4 copies - 2 average
Nihil Spellbomb
4 copies - 2 average
Liliana of the Veil
4 copies - 2 average
Molten Rain
3 copies - 1.5 average
Fulminator Mage
3 copies - 1.5 average
Surgical Extraction
3 copies - 1.5 average