Most played cards in UR:

2 Decks
Lightning Bolt
8 copies - 4 average
Volcanic Island
8 copies - 4 average
Serendib Efreet
8 copies - 4 average
Chain Lightning
8 copies - 4 average
Counterspell
8 copies - 4 average
Shatter
7 copies - 3.5 average
Red Elemental Blast
7 copies - 3.5 average
Psionic Blast
6 copies - 3 average
Strip Mine
6 copies - 3 average
Mishra's Factory
6 copies - 3 average
Fireball
4 copies - 2 average
Power Sink
4 copies - 2 average
Mind Control
4 copies - 2 average
Energy Flux
4 copies - 2 average
Stone Rain
3 copies - 1.5 average
City of Brass
3 copies - 1.5 average
Blue Elemental Blast
2 copies - 1 average
Fork
2 copies - 1 average
Library of Alexandria
2 copies - 1 average
Mox Ruby
2 copies - 1 average