I'm going with the P-38. Everyone picks the P-51D but i think the P-38 was just as good. I'll name my favorite bombers/fighters for each conflict.

WWII: P-38, Ju-88/B-17

Korea: F-86, B-29

Vietnam: F-4 Phantom(Navy Version) B-52

Desert Storm:F-15C, F-117A- The F-117 while only able to carry a small bomb load (2x2,000 lb Bombs) was absolutely integral in penetrating the very large and sophisticated Anti-Aircraft battery, though the AH-64 Apache took out the very first radar sites in Desert Storm.

Operation Enduring Freedom:F/A-18, B-52

Operation Iraqi Freedom: F-15E Strike Eagle, B-2


As far as attack helicopters go i'd love to see the the AH-1Z King Cobra and the RAH-66 Comanche. It's to bad they ended the Comanche program, that was def. a huge jump in helicopter technology.