Most played cards in Dragon:

3 Decks
Bazaar of Baghdad
12 copies - 4 average
Worldgorger Dragon
10 copies - 3.33 average
Jace, Vryn's Prodigy
9 copies - 3 average
Underground Sea
9 copies - 3 average
Polluted Delta
9 copies - 3 average
Animate Dead
7 copies - 2.33 average
Collective Brutality
6 copies - 2 average
Thoughtseize
6 copies - 2 average
Null Rod
5 copies - 1.67 average
Dance of the Dead
5 copies - 1.67 average
Flooded Strand
4 copies - 1.33 average
Force of Will
4 copies - 1.33 average
Flusterstorm
4 copies - 1.33 average
Bloodstained Mire
4 copies - 1.33 average
Gitaxian Probe
4 copies - 1.33 average
Abrupt Decay
4 copies - 1.33 average
Tasigur, the Golden Fang
4 copies - 1.33 average
Intuition
4 copies - 1.33 average
Leyline of the Void
4 copies - 1.33 average
Pull from Tomorrow
4 copies - 1.33 average