Most played cards in UW Control:

3 Decks
Counterspell
12 copies - 4 average
Tundra
12 copies - 4 average
Swords to Plowshares
12 copies - 4 average
Disenchant
12 copies - 4 average
Mishra's Factory
12 copies - 4 average
Serra Angel
10 copies - 3.33 average
City of Brass
8 copies - 2.67 average
Underground Sea
8 copies - 2.67 average
Jayemdae Tome
8 copies - 2.67 average
Blue Elemental Blast
7 copies - 2.33 average
Divine Offering
6 copies - 2 average
Power Sink
6 copies - 2 average
Control Magic
6 copies - 2 average
Serendib Efreet
4 copies - 1.33 average
Maze of Ith
4 copies - 1.33 average
Savannah Lions
4 copies - 1.33 average
Brass Man
4 copies - 1.33 average
Wrath of God
4 copies - 1.33 average
Dust to Dust
4 copies - 1.33 average
Braingeyser
3 copies - 1 average