Most played cards in Rakdos:

5 Decks
Bloodstained Mire
20 copies - 4 average
Inquisition of Kozilek
19 copies - 3.8 average
Blood Moon
18 copies - 3.6 average
Fatal Push
17 copies - 3.4 average
Marsh Flats
16 copies - 3.2 average
Terminate
16 copies - 3.2 average
Blackcleave Cliffs
14 copies - 2.8 average
Thoughtseize
13 copies - 2.6 average
Kolaghan's Command
12 copies - 2.4 average
Leyline of the Void
12 copies - 2.4 average
Anger of the Gods
10 copies - 2 average
Blood Crypt
10 copies - 2 average
Liliana of the Veil
9 copies - 1.8 average
Goblin Rabblemaster
8 copies - 1.6 average
Dark Confidant
8 copies - 1.6 average
Mutavault
8 copies - 1.6 average
Demigod of Revenge
8 copies - 1.6 average
Dragon's Claw
7 copies - 1.4 average
Fulminator Mage
6 copies - 1.2 average
Faithless Looting
6 copies - 1.2 average