Most played cards in UG Fog:

4 Decks
Brainstorm
16 copies - 4 average
Accumulated Knowledge
16 copies - 4 average
Moment's Peace
16 copies - 4 average
Jace's Erasure
16 copies - 4 average
Tangle
16 copies - 4 average
Arcane Denial
16 copies - 4 average
Muddle the Mixture
13 copies - 3.25 average
Ponder
12 copies - 3 average
Respite
12 copies - 3 average
Nourish
12 copies - 3 average
Take Inventory
8 copies - 2 average
Scattershot Archer
8 copies - 2 average
Evolving Wilds
8 copies - 2 average
Ash Barrens
8 copies - 2 average
Thornwood Falls
8 copies - 2 average
Dispel
7 copies - 1.75 average
Quiet Disrepair
6 copies - 1.5 average
Miscalculation
4 copies - 1 average
Relic of Progenitus
4 copies - 1 average
Think Twice
4 copies - 1 average