Some of the players mentioned in this thread were poor signings with hindsight, but at the time I don't remember many complaints about signing players like Rothen, Guivarc'h etc.
For the most bizarre signings, it's pretty much take your pick from any of McCoist's apart from the few successes. How anyone would think signing players like Cribari or Faure the lower leagues in Scotland was a good idea, i'll never know.