I don't know that I have a favorite breed yet. And I don't know that I will ever be able to choose just one. Right now I'm really liking my blue orpington hen. She's huge, gentle, very diplomatic with the rest of the flock (I suspect she's top hen, if not top of the pecking order than very near the top), and lays large eggs very regularly. I also really like my speckled sussex hens. The downsides to them is that they are a little too friendly sometimes, always in the way if they think food might be involved, and they don't lay as large an egg as any of my other girls (although they do lay fairly regularly also). But the one hen that I think we might end up keeping even after her days as a productive layer are over because we just really like her a lot is my EE hen. She was the first chicken I had to start laying, her eggs are large and she lays very well. She's friendly, although not cuddly by any means, and just an all around good chicken.
Of course there are so many breeds I would like to "try" but haven't had the time yet. Faverolles, Dorkings, Marans, and Frizzles (just for fun) are probably on the top of my breed "wish list" for the future. But I would probably be happy to try just about any breed. If I had more land, the flightier Mediterranean breeds like the leghorn or andulusian could be a lot of fun. And I haven't even seriously given bantams much thought because that makes the choices and options just too overwhelming for me.