Most played cards in U/W control:

2 Decks
Force of Will
8 copies - 4 average
Brainstorm
8 copies - 4 average
Swords to Plowshares
8 copies - 4 average
Spell Snare
6 copies - 3 average
Scalding Tarn
5 copies - 2.5 average
Flooded Strand
5 copies - 2.5 average
Sensei's Divining Top
4 copies - 2 average
Tundra
4 copies - 2 average
Jace, the Mind Sculptor
4 copies - 2 average
Counterspell
4 copies - 2 average
Snapcaster Mage
4 copies - 2 average
Counterbalance
3 copies - 1.5 average
Cunning Wish
3 copies - 1.5 average
Thopter Foundry
3 copies - 1.5 average
Peacekeeper
3 copies - 1.5 average
Spell Pierce
3 copies - 1.5 average
Tormod's Crypt
2 copies - 1 average
Surgical Extraction
2 copies - 1 average
Enlightened Tutor
2 copies - 1 average
Plateau
2 copies - 1 average