Most played cards in Mono Blue Control:

3 Decks
Threads of Disloyalty
10 copies - 3.33 average
Spell Snare
8 copies - 2.67 average
Ancestral Vision
8 copies - 2.67 average
Hurkyl's Recall
8 copies - 2.67 average
Thirst for Knowledge
7 copies - 2.33 average
Vedalken Shackles
7 copies - 2.33 average
Stifle
7 copies - 2.33 average
Engineered Explosives
7 copies - 2.33 average
6 copies - 2 average
Cryptic Command
6 copies - 2 average
Tarmogoyf
4 copies - 1.33 average
Spellstutter Sprite
4 copies - 1.33 average
Mutavault
4 copies - 1.33 average
Mana Leak
4 copies - 1.33 average
Condescend
4 copies - 1.33 average
Urza's Mine
4 copies - 1.33 average
Urza's Power Plant
4 copies - 1.33 average
Urza's Tower
4 copies - 1.33 average
Remand
4 copies - 1.33 average
Gifts Ungiven
4 copies - 1.33 average