What do you all consider your list of "field tools"? My tractor is currently remote and hiding on a tract of land. I have no way of servicing it out there except laying on the ground or load it on the hauler and work on it there. (The equipment barn is being built in another month or two). I try and inspect before use looking for anything loose but bolts you don't expect to find loose (and rarely check) have either lost the nut and sometimes the bolt too. The HW store is a 40 mile round trip. I've taken to buying extras in case any others fall out. The anti-slip washers Mahindra put on are crap. I've been replacing them with not just a lock washer but also a nylon-insert locking nut on top of that.
Once the equipment barn is up, I plan on drilling a set of the common "problem bolts" and using safety wires or cotter pins. At least if they come loose, I won't drop hardware in the field.