When I'm in my own area I usually just carry the stock jack, a fire extinguisher (in all my vics, since they are cheap insurance). When I'm on the road, I'll fill up an ammo box with (std or metric) tools, maybe a small hydraulic jack.
Most important, I carry my AAA card.
When I'm dragging a trailer, I keep a spare hub with me. I also toss in a few 4x4's or 4x6's to use as a trailer jack,, just pull the trailer tire up on them and the other axle is hanging.
