While reading through the thread Tools that are much better than you expected Started by Thomas Marr, (now on page two, below) I wondered if anyone had asked the obvious question: what was your worst purchase? A quick search showed several - starting with one by Rick Potter in 2007: http://www.sawmillcreek.org/showthre...tool-purchases .
Several people responding then mentioned the roto-zip. I have one: $10 at a garage sale and I got ripped off because it cuts gyprock beautifully, but throws a rooster tail that annoys the whole neighborhood and creates days of cleanup work.
Anyone want to confess to doing worse than that?