Most played cards in Gruul:

4 Decks
Lightning Bolt
16 copies - 4 average
Burning-Tree Emissary
16 copies - 4 average
Pyroblast
13 copies - 3.25 average
Nest Invader
12 copies - 3 average
Electrickery
11 copies - 2.75 average
Nettle Sentinel
8 copies - 2 average
Kird Ape
8 copies - 2 average
Living Totem
8 copies - 2 average
Thermo-Alchemist
8 copies - 2 average
Scatter the Seeds
8 copies - 2 average
Rugged Highlands
8 copies - 2 average
Khalni Garden
8 copies - 2 average
Sprout Swarm
8 copies - 2 average
Dynacharge
8 copies - 2 average
Terramorphic Expanse
8 copies - 2 average
Flame Slash
7 copies - 1.75 average
Wild Mongrel
7 copies - 1.75 average
Rancor
6 copies - 1.5 average
Essence Warden
6 copies - 1.5 average
Relic of Progenitus
6 copies - 1.5 average