Definately the G4 iMac. It's so good for apple. Just like the origional iMac. All the people that origionally got them dont need an upgrade but this might make them get it. Also, its a new really cool design and has been getting really good press. People are biting. In fact my cousin is getting on instead of a dell laptop thanks to me.
TiPB - while the G4 iMac has some wow appeal, it still looks a little like a toy. First hand experience has shown me that when I pull out the TiPB at a meeting or with a client that hasn't seen one before, it blows them away.