Most played cards in Doomsday Maniac:

5 Decks
Underground Sea
19 copies - 3.8 average
Flusterstorm
17 copies - 3.4 average
Preordain
17 copies - 3.4 average
Doomsday
17 copies - 3.4 average
Force of Will
16 copies - 3.2 average
Mental Misstep
15 copies - 3 average
Gush
14 copies - 2.8 average
Polluted Delta
13 copies - 2.6 average
Trygon Predator
11 copies - 2.2 average
Dark Ritual
11 copies - 2.2 average
Thoughtseize
10 copies - 2 average
Misty Rainforest
10 copies - 2 average
Gitaxian Probe
8 copies - 1.6 average
Leyline of the Void
8 copies - 1.6 average
Duress
8 copies - 1.6 average
Hurkyl's Recall
8 copies - 1.6 average
Tropical Island
6 copies - 1.2 average
Flooded Strand
6 copies - 1.2 average
Laboratory Maniac
5 copies - 1 average
Sensei's Divining Top
5 copies - 1 average