3) Custom Foam Cut Outs. I made custom foam cut outs for every piece of gear I have in my road case. They serve 2 purposes really: first of which is that everything is protected by it's own space. The second of which is that after I finish a set I might have had a little too much to drink at times, and it becomes a game of making sure I have all my gear by making sure every hole is filled. I call it "Drunk Puzzle."
4) Extra cables, power supplies, etc.. I carry a duplicate of every cable I need just in case one dies, or got damaged during travel.
5) Extra earplugs. I have a nicer pair that always stay with me in my pocket, but sometimes they get forgotten at the hotel, so I have a big pack of just cheap foam ear plugs in the bottom of my case for those occasions where I forgot my nicer ones.