Most played cards in Smog Combo:

2 Decks
Brainstorm
8 copies - 4 average
Chain of Smog
8 copies - 4 average
Ponder
8 copies - 4 average
Thoughtseize
7 copies - 3.5 average
Misty Rainforest
7 copies - 3.5 average
Polluted Delta
6 copies - 3 average
Abrupt Decay
5 copies - 2.5 average
Underground Sea
5 copies - 2.5 average
Surgical Extraction
4 copies - 2 average
Veil of Summer
4 copies - 2 average
Summoner's Pact
4 copies - 2 average
Witherbloom Command
4 copies - 2 average
Flusterstorm
4 copies - 2 average
Tropical Island
4 copies - 2 average
Dark Ritual
4 copies - 2 average
Lotus Petal
4 copies - 2 average
Preordain
4 copies - 2 average
Witherbloom Apprentice
3 copies - 1.5 average
Defense Grid
3 copies - 1.5 average
Bayou
3 copies - 1.5 average