Ive got a bunch of tools and spares in my X for that just in case moment on an outing.
I would like to collect a standardized list of what size tools and sockets are needed at a minimum to be able to fix the X on a trail run and am looking for input. That way members can come to this list and see what they need as a start. As you reply, I'll add it to the list below.
This list is in no way the definitive list. Just a good place to start collecting, and a minimum to get you off the trail to the appropriate repair service or Tow truck.

Wrench sizes:
8mm
10mm
12mm
14mm
17mm
18mm
19mm
21mm (suspension/tie rod)
22mm (suspension/tie rod)
Socket Sizes:
10mm reg/deep
17mm reg/deep
18mm reg/deep
19mm reg/deep
21mm reg/deep. (Suspension/tie rod)
22mm reg/deep (suspension/tie rod)
32mm reg (axle nut, Ball joint nut on SPC UCA's)
Hand tools:
Small 1/4" drive socket set with sae/met sizes
Mini sledge Hammer
Deadblow Hammer
Crescent or Adjustable Wrench
Phillips and Flathead Screw drivers, long and short handle
Screwdriver set with numerous tip sizes and security bits
Strap wrench
Breaker bar
Hack Saw
Tin snips
Spanner wrench for coilovers
Vice Grips
Slipjaw pliers
Needle nose pliers
Snap ring pliers
Air tools
Misc.:
Duct Tape
Electric Tape
Self Sealing Hose tape
Cable ties (Tie Wraps)
Spare Fuses
Voltmeter
Matching Spare nuts and bolts in various lengths
Sheet Metal Screws
Movers blanket for laying on while working on X
Tire Irons
Spare valve caps
Tire patch/plug kit (can of tire slime)
Gas/fluid siphon Hose
2 party epoxy for plastic/metal (JB Weld)
Spare roll of electric wire
Assorted solderless connectors
Rechargeable flashlight or headlamp
Tie Wire (metal bailing wire)
Ratchet Strap
550 or 770 cord (Christians Shoelaces)
Assorted Cotter Pins
Small WD40 can
Packets of Red Grease / Lithium Grease
Spare Oil and brake fluid
Blue Loctite
Hi-lift Slider Adapter
Hi-lift style Jack
Small torch
Telescopic Magnet (for when you drop the nut in a place you cant get your hands)
SWR Meter
Funnel for fluids
12v Air Compressor
Small tube cutter
1 Ft sections of steel tube (think Brake hardlines)
Compression fittings for the hardlines
Teflon Tape
Pre cut shrink tube / lighter to shrink the tube
Solder / Soldering pencil
Spare 50amp Winch Fuses
Universal Battery Post cable clamp
Spare Flat Ground Strap
Smal 4ft x 4ft section of clear Plastic sheet (think broken window/rain)
Metal coat Hanger
Hitch mounted Vise
2ft sections 1/2", 5/8", 3/4" sections of rubber hose
Hose clamps and Barbed hose connectors
Exhaust repair clamp
Code Reader
Spare Parts:
CV Joint
Front Driveline Axle (half axle)
Axle Nut
Ball joint boot
Rubber Shock Boot
Oil filter / Air Filter
Universal Joint w/ clips
Spark Plug or two "pre-gapped"
A few Lug Nuts
Serpentine Belt
Radiator Hose
Tie Rods
Belt Tensioner