I'd have to pick the B-26 too. I can't think of many more aircraft in WWII that served as well as the B-26. Plus, it's one of the prettiest planes of all time, with a nice torpedo shaped fuselage.
I'd restore the one currently on static display in France, since I think the flying example should be a later model with the longer wings. However, I tend to think the USAFM should always have one on static display and that Flak Bait at the NASM is much too historic to risk flying again...so we're left with the French one (sorry, France).
For a paint scheme, I think I'd go with "Mild and Bitter". A little history of Mild and Bitter pulled from the 'net (written by J.K. Havener):
"It [the B-26] was the first Allied bomber in the European Theater of Operations to complete 100 operational missions. This was accomplished by Mild and Bitter on an afternoon raid on a Nazi airfield at Evreux/Fauville, southwest of Rouen, France, on 9 May 1944. She was a B-26B-25, Serial Number 41-31819, of the 450th Squadron in the 322nd Bomb Group (M) of the 9th Air Force and had flown her first mission on 23 July 1943. She did all this on her original engines, amassing a total of 449 hours and 30 minutes on them, 310 hours and 40 minutes of that in combat! During this time she never aborted due to mechanical failure, and not one of her many crewmen was a casualty."
A bunch of B-26 firsts are mentioned here (where I got the info about Mild and Bitter):
http://www.billsb-26marauder.org/b26_firsts.htm