When your in metropolis get a warthog or a ghost and take it all the way to the last part (the giant scarab). When the scarab stops and cortona says you're gonna have to board the scarab. Get the Ghost or Warthog on top of the Scarab and get out. Then the warthog or ghost will float with no one in it and if you hit the side of one of them, it will spin out of control in the same place. I dont know if any one has found this, but I thought it was really cool so I posted it.