gismo
     n 1: something whose name is either forgotten or not known syn:
          dohickey, dojigger, doodad, doohickey, gimmick,
           hickey, gizmo, gubbins, thingamabob, thingumabob,
           thingmabob, thingamajig, thingumajig, thingmajig,
           thingummy
     2: a device that is very useful for a particular job syn: appliance,
         contraption, contrivance, convenience, gadget, gizmo,
         widget
see also:
dohickey dojigger doodad doohickey gimmick hickey 
gizmo gubbins thingamabob thingumabob thingmabob 
thingamajig thingumajig thingmajig thingummy appliance 
contraption contrivance convenience gadget widget