I don't have a packing list, but I pack light and season dependent. My checked luggage, I don't put a lock on as I don't pack anything in that bag that cannot be easily replaced. My last trip, somewhere, DFW, DOH, or JNB (I suspect JNB) my bag was opened and rummaged through, but nothing missing. I know because they left my toiletry kit was opened and left unzipped. Do I sometimes forget things, yes. This last trip its was a flashlight and my Gautrain card, but I managed without those things - flashlight on iPhone and did not take the train to Sandton or Rosebank and just stayed in the Airport.
The most important thing to take is your own personal pharmacy. If you change in Europe or the UK, you can pack about anything. If you change in the Middle East you have to be careful what you bring. For example, Sudafed is a controlled substance and you can find yourself on an extended vacation away from home.
Your gun case will need a lock in every lock hole.