Most played cards in Ad Nauseam:

1 Decks
Misty Rainforest
4 copies - 4 average
Thoughtseize
4 copies - 4 average
Brainstorm
4 copies - 4 average
Cabal Ritual
4 copies - 4 average
Dark Ritual
4 copies - 4 average
Lion's Eye Diamond
4 copies - 4 average
Lotus Petal
4 copies - 4 average
Polluted Delta
4 copies - 4 average
Infernal Tutor
4 copies - 4 average
Preordain
4 copies - 4 average
Ponder
4 copies - 4 average
Abrupt Decay
3 copies - 3 average
Underground Sea
2 copies - 2 average
Echoing Truth
2 copies - 2 average
Surgical Extraction
2 copies - 2 average
Hurkyl's Recall
2 copies - 2 average
Flusterstorm
2 copies - 2 average
Wishclaw Talisman
2 copies - 2 average
Duress
2 copies - 2 average
Veil of Summer
2 copies - 2 average