Most played cards in TwiddleVault:

2 Decks
Twiddle
8 copies - 4 average
Howling Mine
8 copies - 4 average
Counterspell
6 copies - 3 average
Hurkyl's Recall
5 copies - 2.5 average
Recall
5 copies - 2.5 average
Copy Artifact
5 copies - 2.5 average
Su-Chi
4 copies - 2 average
Mishra's Factory
4 copies - 2 average
Blue Elemental Blast
4 copies - 2 average
Tropical Island
4 copies - 2 average
Time Vault
4 copies - 2 average
City of Brass
3 copies - 1.5 average
Transmute Artifact
3 copies - 1.5 average
Boomerang
3 copies - 1.5 average
Black Vise
3 copies - 1.5 average
Triskelion
3 copies - 1.5 average
Sylvan Library
3 copies - 1.5 average
Volcanic Island
3 copies - 1.5 average
Tranquility
2 copies - 1 average
Braingeyser
2 copies - 1 average