Well technically I wasn't on the bike when I fractured my skull. I suppose that's the worst.
Lots of lighter moments. Misjudging a corner hung over and splatting, cartoon style, into a sandtone wall like a human fly. Banging into the gate that normally opened, with my feet still in my toeclips, to find that it didn't and slowly toppling sideways in front of a bus queue of people. Gently coasting towards some temporary lights head down to discover when I looked up the lights were right in front of me and my only option was to embrace them and slide down in an untidy heap.
A few desperate bonks, including one where I just had reached the point I couldn't function, rolling past refreshment stops just unable to tell myself to stop and then just about managing at the last place and then finding I couldn't focus to read the menu and just pointing and asking for tea as well. When the world swam into view I had a chicken pie and some apple crumble (not on the same plate) and no memory of the last 15 miles and thousands of midge bites where I'd fallen into a ditch and just lay there.
But mostly, not many bad memories and even the bad ones have some light relief.