What Pokemon can evolve by trading?

Answer 1

There were 4 Pokemon that evolved by trading in the first generation and these Pokemon have been in just about every Pokemon game ever since, so more people will buy the game and trade with each other. The 4 classics are Kadabra, Haunter, Machoke and Graveler. However there are some Pokemon that need to be traded with a specific item to evolve. Like Onix and Scyther holding the Metal Coat. Poliwhirl, Seadra and Slowpoke holding the Kings Rock. And Clampearl holding either the Deepsea Scale or Deepsea Fang (I think its Fang, at least something sharp :P) and there's a few others that I can't remember right now. Hope this helps you out :).