Some home poker games and some casinos play the double ace flush rule, in which a wild card in a flush always plays as an ace, even if one is already present. In such a game, the hand A-Wild-9-5-2 (of one suit) would play as if it were A-A-9-5-2, defeating A-K-Q-10-8, whereas by the standard rules it would play as A-K-9-5-2 and therefore lose (the opposing hand's Q outranks the former's 9). This rule is rare, and is an exception to standard practice, so it should be announced clearly if you intend to use it.

See also: Poker