Most played cards in U/W Control:

2 Decks
Prairie Stream
8 copies - 4 average
Port Town
8 copies - 4 average
Spell Queller
8 copies - 4 average
Mausoleum Wanderer
8 copies - 4 average
Rattlechains
8 copies - 4 average
Selfless Spirit
8 copies - 4 average
Essence Flux
5 copies - 2.5 average
Planar Outburst
5 copies - 2.5 average
Stasis Snare
5 copies - 2.5 average
Ojutai's Command
5 copies - 2.5 average
Clash of Wills
5 copies - 2.5 average
Archangel Avacyn
5 copies - 2.5 average
Summary Dismissal
4 copies - 2 average
Always Watching
4 copies - 2 average
Negate
4 copies - 2 average
Evolving Wilds
4 copies - 2 average
Unsubstantiate
4 copies - 2 average
Tragic Arrogance
3 copies - 1.5 average
Declaration in Stone
3 copies - 1.5 average
Compelling Deterrence
3 copies - 1.5 average