Most played cards in Prison Tron:

4 Decks
Urza's Tower
16 copies - 4 average
Mystic Forge
16 copies - 4 average
Serum Powder
16 copies - 4 average
Karn, the Great Creator
16 copies - 4 average
Urza's Power Plant
16 copies - 4 average
Urza's Mine
16 copies - 4 average
Expedition Map
16 copies - 4 average
Spellskite
16 copies - 4 average
Walking Ballista
16 copies - 4 average
Chalice of the Void
16 copies - 4 average
Ensnaring Bridge
16 copies - 4 average
Thought-Knot Seer
12 copies - 3 average
Eldrazi Temple
12 copies - 3 average
Urza's Saga
10 copies - 2.5 average
Welding Jar
7 copies - 1.75 average
Torpor Orb
6 copies - 1.5 average
Inventors' Fair
6 copies - 1.5 average
Sorcerous Spyglass
5 copies - 1.25 average
Gemstone Caverns
4 copies - 1 average
Sundering Titan
4 copies - 1 average