Most played cards in B/R Aggro:

2 Decks
Lightning Bolt
8 copies - 4 average
Badlands
8 copies - 4 average
Dark Ritual
8 copies - 4 average
Hypnotic Specter
8 copies - 4 average
Black Knight
8 copies - 4 average
Red Elemental Blast
7 copies - 3.5 average
Stone Rain
7 copies - 3.5 average
Sinkhole
6 copies - 3 average
Paralyze
6 copies - 3 average
Black Vise
4 copies - 2 average
Shatter
4 copies - 2 average
Hymn to Tourach
4 copies - 2 average
Mishra's Factory
4 copies - 2 average
Sedge Troll
4 copies - 2 average
Cuombajj Witches
4 copies - 2 average
Sengir Vampire
3 copies - 1.5 average
City of Brass
3 copies - 1.5 average
Terror
3 copies - 1.5 average
Earthquake
2 copies - 1 average
Gloom
2 copies - 1 average