1. (By a distance) C130K 1966 - 2013?
Critical component in East Pakistan evacuation, Belize, Falklands, Ethiopian Relief, Gulf 1&2, FRY, Sierra Leone and Afghanistan. These, plus God knows, how many unknown SF Operations.
2. (Joint) Canberra and Harrier.
Any Post War aircraft the US Government would purchase against the wishes of their own powerful Aviation Lobby has to be good. They have subsequently proved themselves in countless conflicts around the world.
3. Hawk. The only post war aircraft to come in ahead of schedule and under budget. Sold in large numbers to many AF's including our American cousins.
1974- 2040? It will be the longest serving aircraft the Royal Air Force will ever know.
I wager the aircraft will outlast the RAF.