747-400, not only because it's my favorite aircraft, it's perfectly balanced, awe-inspiring, even 1-2 minutes after take-off. In the summer I often sit on my balcony and watch the fat birds take off from FRA. Even before you see 'em coming you can hear it: A deep but not unpleasant roar, a very fat sound, bass frequencies that hit the spot, not shrill, like music. I love it and for me there's no other aircraft that comes even close (Concorde is sheer power, very loud but somewhat "old-fashioned in sound", if you know what I mean).
I know it's only VfB but I like it!