We don't ban certain decks in my playgroup, because FFA is self balancing (if someone pulls a heavy lock or combo in the first game, he may not survive a turn in the next one), and almost half of the table always play some counters in their decks (or swords to plowshares, that's why dragon has never won a game in my playgroup)
My friends and i frequently play FFA T1 and we all know each other's decks...so any deck that is known to be threatening gets stomped on. One of my favorite parts of FFA is the politics and the unintentional alliances that are formed, i found that decks that look innocent and then bust out are the most fun. Right now i'm enjoying the channeler/pemmin's/fireball routine...just wait till people drop their counters and look pathetic while others fight...then drop the cards and fireball everyone off their asses. After that worked a few times everyone is wise to me so i'm probably going to go back to a good ole reanimation deck.