Most played cards in Initiative:

4 Decks
Archon of Emeria
16 copies - 4 average
Cavern of Souls
16 copies - 4 average
White Plume Adventurer
16 copies - 4 average
Seasoned Dungeoneer
16 copies - 4 average
Ancient Tomb
16 copies - 4 average
Wasteland
16 copies - 4 average
Solitude
13 copies - 3.25 average
Chrome Mox
13 copies - 3.25 average
Thalia, Guardian of Thraben
13 copies - 3.25 average
Swords to Plowshares
12 copies - 3 average
Chancellor of the Annex
12 copies - 3 average
Containment Priest
11 copies - 2.75 average
Anointed Peacekeeper
11 copies - 2.75 average
Null Rod
10 copies - 2.5 average
Dauntless Dismantler
9 copies - 2.25 average
Emeria's Call
9 copies - 2.25 average
Loran of the Third Path
9 copies - 2.25 average
Archon of Absolution
6 copies - 1.5 average
Mox Sapphire
4 copies - 1 average
Black Lotus
4 copies - 1 average