My taste has morphed a bit over the years. I used to be absolute in the fact that 3.3" was my ideal blade length for a folder. I still love that length, but now my occupation has changed and I feel fine pulling out any type of knife I want around public really. So I'm in a larger folder kick right now, about 3.6" is around ideal.
As far as models, 2 models come to mind as almost perfect. That would be the BM Bugout and the CRK Large Sebenza (of whatever variety, 21's are my favorite). Both have, in my mind, a very traditional american design style which I've always been partial too. Neither is absolutely perfect in my opinion, though very close. I feel like I could make my own knife that would be about as close to perfect as possible, but I couldn't really describe it in words. It would have a similar shape though to both those two knives.