The absolutely most memorable ones are the bad ones, flying into too bad weather or having some technical stuff, nothing fun to recall, so instead will choose one of very many wonderful trips.
i was flying a customer to their summer cottage in summer weather with local cumulonimbus clouds. We had no hurry, and plenty fuel so we could just fly around the clouds. Outside the clouds the weather was really nice, and flying near clouds that soar miles high in the sky, well, the view just is very beautiful.