There are only seven magic illusions in the entire world - three of them are making something vanish, making something appear, and transformation - turning one item into another.
The Zipper Change Bag can do all three -- with a relatively small object, at least.
A change bag is a nice, versatile prop capable of doing those things, with a zipper on the bottom allowing the magician to unzip the bag and stick his arm through it, to demonstrate that the bag is empty -- even when it really isn't.
It also allows for some comedic play with the audience, as well.
Here are a few examples:

• I'll come on stage holding the change bag, with it already unzipped.
  My partner (or a child from the audience) will point out that "your zipper is open" and I'll do a mini-routine on that, being so embarrassed that I came on stage with my zipper undone!
• Many years ago, at Clown Camp, some of our fellow students did a very funny routine as a pair of inept magicians, trying to turn a silk into a green mouse -- after two failed attempts (remembering the Rule of Three), they finally "succeeded" when they pulled out a rubber frog -- the "green mouse"!
• With the zipper "mistakenly" left open, when putting a red scarf, a white scarf, and a blue scarf into the bag -- with the children yelling that "blue's on the ground!" trying to be helpful -- which I "misinterpret" to be the "magic phrase" that they want me to use -- until the magically-produced flag is missing all of the blue colors, and I then blame the audience for not telling me sooner!Another example of David Ginn's "magician in trouble" routine.
  

Are there drawbacks to the Zippered Change Bag? Of course; for one thing, it's capacity is relatively small, and so only smaller items can be vanished, exchanged, or transformed.
In addition, it is not a prop that can be passed amond the audience -- it is far too easy for a member of the audience to accidentally discover the secret, and turn you into a laughing stock instead of a a magician.
Any time that you need to make a small item vanish, appear, or change places with another small item, the Zipper Change Bag is a natural.
It's large enough to be seen by a large crowd, colorful for the children, packs small, and is extremely versatile.