I remember standing at the side of the road with a flat trailer tire and looking at a rather worthless bumper jack for my grand wagoneer wishing I had a small scissor jack.
channel lock pliers be it for trailer bearings or a make shift dutch oven lid lifter.
wire cutter crimpers for emergency wire repair ( with a few crimps and a small hunk of stranded wire)
I have had my drill along and have used it to power the leveling jacks and happened to have some 3" screws to make repairs to a rather wobbley park picnic table.
4 way lug wrench is almost a must with different trailers and different tow vehicles it's nice to know it will fit where needed.
hammer for tent stakes or whatever!
A small camping axe for tending the campfire and could also sub for the hammer above.
Ratchet straps I never leave home without them. They will keep your first up gazebo on the ground even in high winds, they will also control loose cargo in the pickup on the way. They have even been used to "lock" the coolers shut as protection from the raccoons.