Karns Bastion should be using Proliferate each turn, especially if other, damaging counters are present on the field
Favorites include Dreamscape Artist, Diplomatic Escort, Jaya Ballard, Psychic Frog, Skirge Familiar to add mana, Stronghold Biologist and Machinist to counter creature/noncreature spells, but my two all-stars would be Chamber of Manipulation and Overtaker, turning your land cards into creature-stealing effects for fun and profit
All of the cards in each of these scene boxes are pretty great though, not just FFIX
When Chainer, Dementia Master leaves the battlefield, exile all Nightmares
Cruella de Vil, Fashionable Cruisier is your only real counter, but Launch can be used in a pinch too
Terror Unless you get lucky with matchups, Terror is just way too often a dead card