It is impossible to not love the P-38. If for no other reason than it was used to kill Isoroku Yamamoto.
Close runner ups in my mind would be the SR-71, the A-10 warthog, and the F4U Corsair.
Another gorgeous jet which had much to do with the development of later aircraft was the Douglas F5D Skylancer.
But if I had the means, the one plane I would acquire and learn to fly would be the F86.
This one lives not far from my home.