I carrry way to much. but for a basic kit carry a mix of std and metric wrenches, small, med and big. I seem to use the 13mm a lot on mine. Below is some of the other crap I carry
basic stuff
1st aid kit
Hammer
Vice Grips
Gloves
small tarp in case I break down in mud
shovel
Knife
Multi-tool, such as a leatherman or the like
screw drivers
Torq's set
breaker-bar 3/4
socket set
Flash light
Other crap con't
oil
oil filter
recovery gear, chain, straps, clevis d-rings
u-joints drive shaft
36mm socket for the front hub and the 13mm 12pt wrench for the hub bolts.
spare axle shafts,for dana 30 even though I don't own one anymore..lol
jumper cables
hacksaw
radiator stop leak
rtv blue gasket maker
epoxy
jb weld
tire repair kits
brake parts cleaner
PB Blaster
Gear oil
upper and lower raditor hose's
extra track-bar
extra front steering parts
hand clearner
cotter pins
mixed nuts and bolts
rain gear