Most played cards in Red Deck Wins:

5 Decks
Lightning Bolt
20 copies - 4 average
Flame Javelin
20 copies - 4 average
Figure of Destiny
20 copies - 4 average
Incinerate
20 copies - 4 average
Volcanic Fallout
17 copies - 3.4 average
Goblin Guide
16 copies - 3.2 average
Rift Bolt
16 copies - 3.2 average
Smoldering Spires
15 copies - 3 average
14 copies - 2.8 average
Arid Mesa
12 copies - 2.4 average
Kiln Fiend
12 copies - 2.4 average
Searing Blaze
12 copies - 2.4 average
Scalding Tarn
12 copies - 2.4 average
Plated Geopede
12 copies - 2.4 average
Keldon Megaliths
11 copies - 2.2 average
Magus of the Moon
10 copies - 2 average
Sulfur Elemental
9 copies - 1.8 average
Kargan Dragonlord
8 copies - 1.6 average
Dragon's Claw
8 copies - 1.6 average
Ghostfire
7 copies - 1.4 average