Most played cards in 4 Color Control:

3 Decks
Brainstorm
12 copies - 4 average
Ponder
12 copies - 4 average
Force of Will
12 copies - 4 average
Swords to Plowshares
12 copies - 4 average
Flooded Strand
12 copies - 4 average
Prismatic Ending
10 copies - 3.33 average
Misty Rainforest
8 copies - 2.67 average
Uro, Titan of Nature's Wrath
7 copies - 2.33 average
Tundra
7 copies - 2.33 average
Carpet of Flowers
6 copies - 2 average
Minsc & Boo, Timeless Heroes
6 copies - 2 average
Pyroblast
6 copies - 2 average
Volcanic Island
5 copies - 1.67 average
Force of Negation
5 copies - 1.67 average
Endurance
5 copies - 1.67 average
Life from the Loam
4 copies - 1.33 average
Staff of the Storyteller
4 copies - 1.33 average
Narset, Parter of Veils
4 copies - 1.33 average
Terminus
4 copies - 1.33 average
Orcish Bowmasters
4 copies - 1.33 average