It still astounds me that the RAF Museum's Hurricane is a Battle of France survivor. My 3 most favourite museums in the world (of those I've visited, of course) are:
1. Duxford (flying warbirds, awesome collection and you get to see restoration right before your eyes)
2. Hendon (amazing collection of unique aircraft)
3. Shuttleworth (don't know why but the place sends shivers up my spine - DH-88 Comet, Sopwiths, pre-WWI aircraft, Gladiator...and mostly all airworthy - oh, and the airshows are just a great family event)