I'll second the Hi-Lift jack nomination - we have one for every major vehicle and they have been extremely useful in all sorts of situations. My wife even used the one in her full size van to neatly extricate herself from an entangled accident - she jacked the van up high and pushed it sideways off the jack, neatly clearing the accident by 3 feet. There are lots of useful accessories for Hi-Lift Jacks as well. If you carry the jack externally, learn how to operate the pawl pins manually - rusty, cruddy, dry pins won't walk out automatically. (My jacks are approaching 30 years old - I keep them clean and stored out of the crud nowadays, but there were times...)

Much more expensive but: A winch. I have an ancient Warn 8,000 lbs winch - still the fastest electric winch on the market after over 50 years (heavier than later models, but still the speed champ). Dual batteries and a battery isolator are a must, of course. I use a marine/RV battery that can both deep cycle AND deliver the "starting" amps that the winch draws under load. If I was WORKING with a winch, I would go with a PTO or hydraulic winch, but for purely extraction work and occasional work around the property, an electric is the way to go. If you can't justify the winch, get 2-4 come-alongs, two stout chains with grab hooks, and some cable (for more reach). Slower, but they work well also, IME.

A set of tire chains - good ones - give you a heck of a lot more mobility in difficult situations. Put them on the front tires if you have a 4x4. Stay off the pavement and they DO tear up the ground.

Endless lists... these are just a few tried-and-proven items I've carried/continue to carry.

For the lower-to-the-ground vehicles: Relatively robust scissors jacks are available at automobile junkyards for near scrap-metal prices. They can get you high enough to slip a bottle jack underneath. But carry some PS fluid with you - bottle jacks have a nasty habit of leaking some fluid out if they have been stored in their side for years in a trunk... it's too late to top-off when you need the jack if you don't have some PS fluid with you...

HTH,

Tom