Most played cards in Dragon:

6 Decks
Bazaar of Baghdad
23 copies - 3.83 average
Polluted Delta
22 copies - 3.67 average
Force of Will
20 copies - 3.33 average
Animate Dead
17 copies - 2.83 average
Underground Sea
16 copies - 2.67 average
Worldgorger Dragon
15 copies - 2.5 average
Preordain
15 copies - 2.5 average
Misty Rainforest
14 copies - 2.33 average
Mental Misstep
13 copies - 2.17 average
Ravenous Trap
13 copies - 2.17 average
Squee, Goblin Nabob
11 copies - 1.83 average
Tropical Island
10 copies - 1.67 average
Hurkyl's Recall
8 copies - 1.33 average
Once Upon a Time
8 copies - 1.33 average
Hollow One
8 copies - 1.33 average
Mox Sapphire
6 copies - 1 average
Mox Ruby
6 copies - 1 average
Mox Jet
6 copies - 1 average
Daze
6 copies - 1 average
Collector Ouphe
6 copies - 1 average