If I remember correctly, Hans Rudel's input on ground attack aircraft was used in the development of the A-10.
Notes on U.S. Aces:
WWI: Capt Eddie Rickenbacher (26 victories)
WWII: Major Richard Bong (40 victories)
Korea: Major Joe McConnell (16 victories...also top U.S. jet ace)
Vietnam: See Berny13's post.
Two war Aces (all are USAAF/USAF except the one noted):
Colonel Gabreski : 28 WWII (ETO), 6.5 Korea
Colonel Thyng: 5 WWII, 5 Korea
Colonel Bolt (USMC): 6 WWII (PTO), 6 Korea
LTC Garrison: 7.3 WWII, 10 Korea
Major Whisner: 15.5 WWII (ETO), 5.5 Korea
Major Hagerstrom: 6 WWII, 8.5 Korea
Major Davis: 7 WWII (ETO), 14 Korea