Everybody's situation is different.

My normal habit is to carry a pistol in addition to the shotgun or rifle that I am carrying. If I am expecting some kind of problem(s) to/may arise, then I'll have a 2nd smaller pistol as a backup.

I don't worry about spare parts because my weapons are taken care of and maintained while in the field. Cleaning my weapons each morning occurs before breakfast and while I'm having my first cups of coffee.

I do carry a long knife (KaBar) and a short knife (Buck 110). If I am using my harness, then I'm also carrying a bayonet.

Those are my personal preferences.