13 cards where the text includes “flip a coin” and the text includes “opponent”

Mutalith Vortex Beast (Warhammer 40,000 Commander #134)
Karplusan Minotaur (Coldsnap #86)
Mana Clash (Ninth Edition #203)
Dumb Ass (Unhinged #75)
Fiery Gambit (Mirrodin #90)
Risky Move (Onslaught #223)
Fickle Efreet (Prophecy #89)
Crooked Scales (Mercadian Masques #291)
Goblin Festival (Urza's Destiny #83)
Mogg Assassin (Exodus #88)
Game of Chaos (Fifth Edition #232)
Goblin Lyre (Ice Age #319)
Amulet of Quoz (Ice Age #308)

It is the moment of discovery, the triumph of the mind, and the end of these results.