The UH-60(Blackhawk) is the most purty chopper around, if you want my opinion (which you apperantly do, having asked for it on a forum. Ha ha! I am victorious!)
Course, how could I not love the Spitfire or Lancaster, or, indeed, pretty much all WW2 military aircraft. They are all beautiful.
Modern jets, I think, are not nearly as iconic, though the Eurofighter typoon and the Harrier jump jet are rather, rather nice. The hercules is also damn impressive, especially when one comes up over the crest of a hill on training as you walk along Hadrians wall. That and a Chinnok suddenly appearing over some trees behind me in Snowdonia, about 10 metres up, waving door-gunner and all. Military hardware has a tendancy to be beautiful in its power and might. Tanks, helicopters and guns all seem strangley attractive to me, like a Tiger or a Cheetah.
Maybe that's just me.