Most played cards in Merfolks:

34 Decks
Lord of Atlantis
136 copies - 4 average
Daze
133 copies - 3.91 average
Winter Orb
128 copies - 3.76 average
Gush
124 copies - 3.65 average
Annul
98 copies - 2.88 average
Foil
93 copies - 2.74 average
Counterspell
82 copies - 2.41 average
Merfolk Looter
74 copies - 2.18 average
Waterfront Bouncer
72 copies - 2.12 average
Tidal Warrior
68 copies - 2 average
Blue Elemental Blast
64 copies - 1.88 average
Chill
58 copies - 1.71 average
Rootwater Diver
57 copies - 1.68 average
Quirion Dryad
56 copies - 1.65 average
Gaea's Skyfolk
56 copies - 1.65 average
Stifle
52 copies - 1.53 average
Tormod's Crypt
50 copies - 1.47 average
Yavimaya Coast
50 copies - 1.47 average
Portent
47 copies - 1.38 average
Hydroblast
42 copies - 1.24 average