When closed its the Macbook Air by a mile, but once open the old trackpad and silver bezel spoil it a little.
Ti Powerbook & Al Powerbook (non-unibody) looked great at the time, but they haven't aged well at all IMO, they look so dated when you see one nowadays. As for the Blackbook, that thing looked great out of the box but always looked grubby even after being used for a few mintues, awful choice of material finish which left it looking tacky.
That leaves the Unibody MBP, still the best looking laptop in production, nobody else has come close yet.