Very first Amiga I seen was my brother's Amiga 600, so I have a soft spot for it.... But my favorite is the Amiga 1200.
Though for the longest time I wanted an Amiga 4000.....
I still push around OS 3.0 since thats the roms that are inside my Amiga 1200. Only things I throw on it is magicwb and MUI for the GUI enhancements.