Most played cards in Rakdos:

4 Decks
Dark Ritual
14 copies - 3.5 average
City of Brass
14 copies - 3.5 average
Hypnotic Specter
12 copies - 3 average
Lightning Bolt
12 copies - 3 average
Badlands
12 copies - 3 average
Mishra's Factory
11 copies - 2.75 average
Underworld Dreams
9 copies - 2.25 average
Disenchant
8 copies - 2 average
Red Elemental Blast
8 copies - 2 average
Sinkhole
8 copies - 2 average
Hymn to Tourach
8 copies - 2 average
Scrubland
8 copies - 2 average
Sedge Troll
8 copies - 2 average
The Rack
8 copies - 2 average
Order of the Ebon Hand
7 copies - 1.75 average
Strip Mine
7 copies - 1.75 average
Blood Moon
6 copies - 1.5 average
Gloom
6 copies - 1.5 average
Terror
6 copies - 1.5 average
Chain Lightning
5 copies - 1.25 average