I like some of the jobs by SAAB, and a few of those modern Sukhoi and Mikoyan birds are just beautiful. Shame the Berkut won't be going into service, seeing as the Ruskie air force can't even afford a remotely modern variant of the Flanker.
P-38
P-40
F-86
F-100
F-4
A-1 Skyraider
F-117
MiG-25. Don't know why, but I love it's gigantic engines and intakes. Same goes for the Foxbat.
MiG-21 because I just can't call it ugly.
F-15. The classic symbol of modern US air power, even if the ones we have are falling apart...
Rafael
Eurofighter EF-2000
I dunno, planes just look pretty to me. If it flies, it's beautiful.