Paul Harris has one where he pulls back the flap and removes the deck from the card box...all with ONE HAND!
I saw a guy do a coin-roll type flourish with a box cards.
If you really want to condition your hands to perform these flourishes as if they were child's play, you might consider the following item. It's 8 heavy steel plates in the exact shape as a deck of cards.http://www.penguinmagic.com/search.php?q=pass+trainer
I bought two sets of Pass Trainer so I can practice one-handed cuts and flourishes with both hands independently. Works great!