The warp engine, for the same reasons as Zephram Cochrane (especially the island full of naked women part). At least there was still money to make you rich then. Emory Erickson probably just got a handshake, a pat on the back, his name in the papers, and a new wheelchair. And the transporter would nearly destroy the ground vehicle industry.
Would you rather be seduced by Kirk, Riker, Dax (your choice), or Janeway?