doohickey

from WordNet (r) 3.0 (2006)

doohickey
    n 1: something unspecified whose name is either forgotten or not
         known; "she eased the ball-shaped doodad back into its
         socket"; "there may be some great new gizmo around the
         corner that you will want to use" [syn: {doodad},
         {doohickey}, {doojigger}, {gimmick}, {gizmo}, {gismo},
         {gubbins}, {thingamabob}, {thingumabob}, {thingmabob},
         {thingamajig}, {thingumajig}, {thingmajig}, {thingummy},
         {whatchamacallit}, {whatchamacallum}, {whatsis}, {widget}]

from The Collaborative International Dictionary of English v.0.48

doohickey \doo"hick*ey\, n.
   Any object, usually a tool or other device, whose name is
   forgotten, or not known.

   Syn: thingumbob, whatchamacallit, whachamacallit. [PJC]