In reply to a lakeland climber:
Lee Valley Tools (who specialise in professional cabinetmaking tools) have been designing and producing a one off highly impractical and amusing tool for April Fools Day for ten years now.
(You can see them all,including this year's "Spider Vice" by searching 'AFD' here: www.leevalley.com/en/home/Search.aspx? )
My favourite however, is the "Precision Story Tape":
http://www.leevalley.com/en/wood/page.aspx?p=65357&cat=1,43513
A blank tape measure, that you mark out with a pen off of existing objects... however, it's now actually proved to be a useful enough tool to go on sale.