Just adding to the list here. IMHO the worst tool I've ever purchased was the Roto-Zip Rebel. I'm sure they're great for cutting through sheetrock but try cutting through the backs of kitchen cabinets and all you do is burn up bits. I think I've used it twice and its been sitting in my shed for two years now.
On another note we all know that when a tool bears the Greenlee or Klien label you'll be paying top dollar for it. But I think this one takes the cake. If you carry this in your tool pouch you're telling the world you have $$$ to burn :grin:
http://www.mytoolstore.com/klein/98002bt.html