Most played cards in Junk:

5 Decks
Force of Will
20 copies - 4 average
Brainstorm
20 copies - 4 average
Ponder
20 copies - 4 average
Wasteland
15 copies - 3 average
Polluted Delta
15 copies - 3 average
Force of Negation
13 copies - 2.6 average
Underground Sea
13 copies - 2.6 average
Orcish Bowmasters
12 copies - 2.4 average
Daze
12 copies - 2.4 average
Dragon's Rage Channeler
12 copies - 2.4 average
Murktide Regent
11 copies - 2.2 average
Pyroblast
11 copies - 2.2 average
Volcanic Island
10 copies - 2 average
Lightning Bolt
10 copies - 2 average
Mishra's Bauble
10 copies - 2 average
Flooded Strand
9 copies - 1.8 average
Tamiyo, Inquisitive Student
8 copies - 1.6 average
Psychic Frog
8 copies - 1.6 average
Misty Rainforest
7 copies - 1.4 average
Scalding Tarn
7 copies - 1.4 average