As a nav, the ones I remember are the chances I turned down, eg round the old UK low-level route in a B52 (convinced myself that would be the day a B52 decided to try and fly through Ben Nevis rather than over it), and also a chance to fly with another Nav radar mate on Vulcans who was doing a max bomb drop on the ranges at Episkopi (went to the beach with my crew instead). What an idiot, now I'd pay lots of money for either of those chances.
Didnt turn down a chance to fly in a T4 when the Lightning OCU was temporarily located at Marham though. Brilliant