Most played cards in UWR:

3 Decks
Counterspell
12 copies - 4 average
Tundra
12 copies - 4 average
Disenchant
12 copies - 4 average
Swords to Plowshares
12 copies - 4 average
Serendib Efreet
11 copies - 3.67 average
Volcanic Island
11 copies - 3.67 average
Lightning Bolt
11 copies - 3.67 average
Psionic Blast
11 copies - 3.67 average
Red Elemental Blast
9 copies - 3 average
Chain Lightning
7 copies - 2.33 average
Black Vise
7 copies - 2.33 average
Mishra's Factory
7 copies - 2.33 average
City of Brass
6 copies - 2 average
Plateau
6 copies - 2 average
Serra Angel
6 copies - 2 average
Blue Elemental Blast
6 copies - 2 average
Savannah Lions
4 copies - 1.33 average
Fireball
3 copies - 1 average
Divine Offering
3 copies - 1 average
Strip Mine
3 copies - 1 average