I carry tire repair plugs, sidewall repair patches, some ATF, air compressor, jack, block of wood, and some basic hand tools.
To be fair,I carry stock tj jack with two pieces of 4x4,I scored a Bosch pump when you could still get them(easy to change with access panel)the huge fuel pump box will actually hold the extra denso alternator.but ya,it is a butt load of stuff,but I was able to get a tuffy enclosure for cheap so all of it is secure as long as you lock the tailgate,all of the crap usually stays in the thing 100% of the time.