No cards with text allowed. Only vanilla creatures.
On a more serious note I came up with a format I call "Merchant," which is a team sealed event but both teams put up whatever cards they're willing to trade. Could add a fun political aspect while keeping the games "pure." Also would make decks stronger and there's a strategic aspect to what you show in the trade pool, and what you'll allow to go to the other team. Haven't been able to actually put together a go at it, yet, though.