The 727, 747, P-38, Concorde, and A-10 are among my favorites as well. While the B-29 was perfectly fine airplane in its own right, I'm still partial to the B-17. I have to throw in the P-51D as well.

Now I missed out on some of the gorgeous airliners back in 50s/60s/70s, but as far active civilian aircraft go, I'm quite partial to the 757-200, especially with winglets. Perfectly proportioned, long legs... And after the retirement of the Concorde, it's the best performing airliner out there.