Most played cards in U/R Aggro:

4 Decks
Shivan Reef
16 copies - 4 average
Greater Gargadon
16 copies - 4 average
Incinerate
16 copies - 4 average
Psionic Blast
15 copies - 3.75 average
Mogg Fanatic
12 copies - 3 average
Threaten
12 copies - 3 average
Keldon Marauders
12 copies - 3 average
Mogg War Marshal
11 copies - 2.75 average
Sower of Temptation
11 copies - 2.75 average
10 copies - 2.5 average
Faerie Conclave
9 copies - 2.25 average
Sulfur Elemental
8 copies - 2 average
Rift Bolt
8 copies - 2 average
Rune Snag
8 copies - 2 average
Pyroclasm
7 copies - 1.75 average
Siege-Gang Commander
7 copies - 1.75 average
Keldon Megaliths
7 copies - 1.75 average
Dodecapod
6 copies - 1.5 average
Snow-Covered Mountain
5 copies - 1.25 average
Karplusan Forest
4 copies - 1 average