Most played cards in Mono Blue:

3 Decks
Counterspell
12 copies - 4 average
Serendib Efreet
12 copies - 4 average
Psionic Blast
11 copies - 3.67 average
Blue Elemental Blast
10 copies - 3.33 average
Control Magic
8 copies - 2.67 average
Mishra's Factory
8 copies - 2.67 average
Energy Flux
7 copies - 2.33 average
Unstable Mutation
6 copies - 2 average
Strip Mine
6 copies - 2 average
Juggernaut
4 copies - 1.33 average
Power Sink
4 copies - 1.33 average
Su-Chi
4 copies - 1.33 average
Hurkyl's Recall
4 copies - 1.33 average
Flash Counter
4 copies - 1.33 average
Dandân
4 copies - 1.33 average
Psychic Purge
4 copies - 1.33 average
Flying Men
4 copies - 1.33 average
Dandan
4 copies - 1.33 average
Phantasmal Forces
4 copies - 1.33 average
Mana Drain
3 copies - 1 average