Most played cards in 4c Tron:

2 Decks
Urza's Power Plant
8 copies - 4 average
Urza's Mine
8 copies - 4 average
Mulldrifter
8 copies - 4 average
Urza's Tower
8 copies - 4 average
Prophetic Prism
8 copies - 4 average
Expedition Map
7 copies - 3.5 average
Moment's Peace
7 copies - 3.5 average
Hydroblast
6 copies - 3 average
Mnemonic Wall
5 copies - 2.5 average
Dinrova Horror
4 copies - 2 average
Mystical Teachings
4 copies - 2 average
Swiftwater Cliffs
4 copies - 2 average
Gorilla Shaman
4 copies - 2 average
Thornwood Falls
3 copies - 1.5 average
Electrickery
3 copies - 1.5 average
Pyroblast
3 copies - 1.5 average
Flame Slash
3 copies - 1.5 average
Fangren Marauder
3 copies - 1.5 average
Dispel
3 copies - 1.5 average
Shimmering Grotto
3 copies - 1.5 average