Cut a Deck of Cards With One Hand

Next time somebody tells you, "Cut the Cards", make them worry that you know more than you let on.

Steps

Start with a nice even deck of standard playing cards. A deck with too many bent cards will make this look sloppy.
Place entire deck between your first and middle finger, as far down in the V as comfortable, so the cards rest at the joint closest to your hand.
Have the inside of your hand face you.
Bring your thumb to the front of deck and slide the top half of the deck over to your thumb.
As the top deck slides over, use the same two fingers to let the bottom half slip to its side, while holding the top half with your first finger and thumb.
Remove your pointer finger from between cards and let the two halves come together again.
You should now have cut the deck!

New cards tend to be slippery and may make them fall from your hands before you are able to get them back together.
Small, child size hands have a harder time with this trick than adult sized hands.
Poker etiquette dictates that the dealer places the deck on the table in front of the player to cut (the player right of the dealer). The 'cutter' takes a portion of the deck from the top and places them between the bottom portion and the dealer. The dealer then places the bottom portion on top of the cut and deals the cards.