Most played cards in U/R Tron:

4 Decks
Thirst for Knowledge
12 copies - 3 average
Remand
12 copies - 3 average
Gifts Ungiven
12 copies - 3 average
Repeal
12 copies - 3 average
Fire // Ice
12 copies - 3 average
Urza's Tower
11 copies - 2.75 average
Condescend
11 copies - 2.75 average
Izzet Signet
11 copies - 2.75 average
Urza's Power Plant
11 copies - 2.75 average
Urza's Mine
11 copies - 2.75 average
Tolaria West
10 copies - 2.5 average
Steam Vents
9 copies - 2.25 average
Chrome Mox
9 copies - 2.25 average
Mindslaver
8 copies - 2 average
Triskelion
7 copies - 1.75 average
Engineered Explosives
6 copies - 1.5 average
Sundering Titan
6 copies - 1.5 average
Hurkyl's Recall
5 copies - 1.25 average
Tormod's Crypt
5 copies - 1.25 average
Polluted Delta
4 copies - 1 average