An A2000 - amiga at the height of its funding & development. Built solid, hard to break it, fun project machine - it can do a lot of stuff. Before you say "what about a3000 / a4000?" I still have one of each (a3k, a4k), and they are good machines, but the big box a2000 captures the spirit of amiga.
My fave is the A1200, personally, but I believe that the A2000 captures the essence of "Amiga."