My pack list
Local parks,schools etc.:
cell phone,MD,extra battery/batteries,PP w/extra battery,digger,pouch,golf club cleaning brush (has both stainless steel and nylon bristles),garden pruner for roots,pocket knife,a snuff can for the smaller good finds,if it's wet I'll bring knee pads,gloves,(one or two times ripping a finger open on can slaw,glass or rusty sharp iron will make you remember to bring those),1st aid kit in case you don't...lol,maybe a snack or two.
being that the vehicle is usually close in these spots I don't pack around the extra batteries,first aid kit,or bring water since there's usually a fountain in these type spots unless you're a freak about drinking from a public fountain.
Woods,fields,off the beaten paths:
besides the list above a lunch,ice chest with cold waters,liquid refreshments,shovel,insect repellent,if sunny a wide brim hat and sunscreen.my back up detector...nothing worse than driving an hour or two to a spot and have your detector go on the fritz,and it has happened to me,fortunately I had my back up that time or else the day would have been ruined for two of us.