But seriously, I'm looking for the things that you might need in-flight at the spur of the moment, for which you did not and maybe could not prepare.
Cup of coffee - and one of those little plastic bags to get rid of it
OK, OK, BP, you didn't really expect serious answers, no ?
I'll try regardless: mine contains checklist, the plog for the flight with frequencies (both comms and nav) and the plates for departure/arrival as well as possible alternates/diversions. The latter kept to a realistic minimum, after all my GPS has a 'Nearest' button. Ouch, now I said it again......