Thanks for mentioning the color-changing knives. I use them in almost every close-up performance, and they are a natural break from cards.
A knife is an understandable, if no longer common, thing to carry--especially for a man. They have a non-magic shop naturalness in that they are familiar day to day objects that anyone might carry--like a pen, handkerchief, ring, or set of keys.
After these, we quickly run out of "natural" personal objects to introduce into a magic routine.
They are more a classic than a cliche in my opinion, and even with the over-familiarity that magicians have with them, they are still fresh and effective in performance for "real people."
Besides which, I have many times been grateful to have a set on me when a package needed opening, a string cut, or a dangling thread removed...
[ August 23, 2001: Message edited by: Whit Haydn ]