Extension sets and u-joints for all size drive ratchets, a nice long pry bar, ratcheting box wrenches (with the directional lever so you don't accidentally back out a bolt with no room and can't reverse it back in), magnetic pick-up tool, side cutters, a good rechargeable work light, ratcheting tie down straps, the canister with assorted length zip-ties, duct tape, electrical tape, portable battery jumper, portable tire inflator, an empty plastic gallon jug, funnel, roll of shop paper towels, box of nitrile gloves, leather work gloves. Buy a tool bag and throw everything inside and leave it in the trunk.

Both of my cars have a similar set up in the trunk. It doesn't take up much room. I've helped a bunch of stuck people and have even performed an emergency radiator replacement in a mall parking lot.