Like everybody else I can't list a single choice.
same here. This is my list in order of preference
1. F-104 Starfighter - Not the most funny airplane to fly at the beginning but it rewarded you more and more with experience.
2. B707-320 - In some respect similar to the 104. Not the easiest airplane to fly but, once you got to grips with it, a real sweetheart.
3. T-38 - Just easy and beautiful!
Cheers,
mad