Most played cards in U/W Control:

4 Decks
Path to Exile
14 copies - 3.5 average
Spell Snare
14 copies - 3.5 average
Baneslayer Angel
13 copies - 3.25 average
Mana Leak
12 copies - 3 average
Kitchen Finks
12 copies - 3 average
Meddling Mage
11 copies - 2.75 average
Hallowed Fountain
10 copies - 2.5 average
Wrath of God
9 copies - 2.25 average
Scalding Tarn
8 copies - 2 average
Cryptic Command
8 copies - 2 average
Tolaria West
8 copies - 2 average
Engineered Explosives
8 copies - 2 average
Ancestral Vision
8 copies - 2 average
Mystic Gate
8 copies - 2 average
Glacial Fortress
7 copies - 1.75 average
Misty Rainforest
7 copies - 1.75 average
Day of Judgment
7 copies - 1.75 average
Glen Elendra Archmage
7 copies - 1.75 average
Chalice of the Void
6 copies - 1.5 average
Repeal
6 copies - 1.5 average