Most played cards in Captain America:

2 Decks
Compulsive Research
8 copies - 4 average
Court Hussar
8 copies - 4 average
Lightning Angel
8 copies - 4 average
Lightning Helix
8 copies - 4 average
Wrath of God
8 copies - 4 average
Hallowed Fountain
7 copies - 3.5 average
Sacred Foundry
7 copies - 3.5 average
Firemane Angel
6 copies - 3 average
Sulfur Elemental
6 copies - 3 average
Flagstones of Trokair
6 copies - 3 average
Demonfire
6 copies - 3 average
Faith's Fetters
5 copies - 2.5 average
Detritivore
5 copies - 2.5 average
Azorius Signet
4 copies - 2 average
Steam Vents
4 copies - 2 average
Boros Signet
4 copies - 2 average
Take Possession
4 copies - 2 average
Pithing Needle
3 copies - 1.5 average
Temporal Isolation
3 copies - 1.5 average
Condemn
3 copies - 1.5 average