This has been a fun thread to follow. I find "10 essentials" kits to be the ideal solution.
Two things to add...
1) I keep my 10 essentials spread across 2 inexpensive Outdoor Products fanny packs that I've cut the hip belts off of. Ideal little organizers. I keep them both in a day back that rides in the back of my car, doing double duty as a car emergency kit. On any trip into the woods, all I need to do is ensure those 2 organizers make into the pack I'm using on that trip, and I'm set. I'll post my 10 essential list at the end, since we're all sharing.
2) I consider rule #1 to be filing a "flight plan". This can be a phone message or a note left on my dashboard. I know a guy from another forum (VFTT - a New England oriented hiking forum) who went out on a moderate backcountry XC loop that started and ended on the very heavily used Waterville Valley trail system. At the point farthest out from the maintain and patrolled trails (about 4 miles in) he hooked a ski tip and suffered a double spiral fracture of his femur. He reported being entirely incapacitated with pain - so much so that he was unable to remove his day pack to retrieve his high loft belay parka or his satellite phone, both of which he carried for emergency. By luck, there was one more party on that loop and he was found at dusk and hours later was taken out by ski-doo to face 2 surgeries to repair the bone.
I solo hike and ski all the time. Lots of reasons. But Doug's story is a harsh reminder of how bad thing can go and how fast they can get there. IMO, if you have family and loved ones, they (not us, but they) deserve that we file flight plans so they can find our body if things don't go well.
My essentials kit...
ESSENTIAL KIT
Basic tools
+ Map (typically moved to pants pocket)
+ Compass (in my pocket when off trail)
+ Altimeter watch (moved to wrist)
+ Lighter
+ Pocket knife (Opinel)
+ Leatherman Squirt PS4 (for small pliers and scissors, mainly)
+ Keychain flashlight on a lanyard (I wear this as a necklace at night)
Chemicals- Carried in a separate ziplock
+ Sun screen
+ Dermatone (in winter)
+ Bug dope
+ Ibuprofen
+ Iodine water purification tablets (water filter is carried separately on some trips)
Toiletries
+ Toothbrush and toothpaste (these are kept in a ziplock bag)
+ Toilette paper, hand sanitizer, disposable lighter (these are kept in a ziplock bag)
Repair kit - Carried in a separate ziplock
+ Spare Fastex 2" buckle (for backpack hip belts)
+ Section of adhesive nylon repair tape (for down jackets, bags and tents)
+ Heavy polyester thread, standard needle and curved upholstery needle
+ Spare stove filler cap (I typically carry a Svea 123 and this is the only part to fail)
+ Spare batteries (for headlamp)
+ Small roll of duct tape (wrapped around a cut-off disposable pen body
Emergency Gear
+ Headnet
+ Whistle
+ Folding saw (Carried October through April)
+ Mylar aluminium bivy sack/shelter
+ 2 Powerbars (emergency food)
+ Coil of parachute chord
Minimal 1st aid kit - Mostly focused on stopping bleeding and attending to feet
+ Antihistamines
+ Selection of gauze pads and band aids
+ Butterfly tape and small roll of bandage tape
+ Gauze wrap
+ Alcohol wipes, iodine wipes, small tube of triple-biotic ointment
+ Disposable razor (shaving shins)
+ Pre-cut moleskin and bottle of Skin Shield (for blisters)
+ Nail clippers, fine tweezers (splinters), Leatherman PS4 (scissors, pliers)
+ Spare disposable lighter