For a Jag-Stang, it depends on what version you have. I have the earlier run that was Basswood (later ones are Alder or so I'm told).
The Basswood ones, because of the body wood, light bridge density, brass saddles, and short scale, they tend to have a naturally good scooped midrange so something that enhances the midrange or upper midrange would be an excellent choice. I'd think a DiMarzio Super II would sound good in one of the old basswood ones like mine if you want a more vintagey sound, and something more like a Stag Mag would work on the higher output end of passive pickups.
The later ones, because of the decreased low-end response from an Alder body, probably want to throw something with slightly more lows than above into the picture, maybe like a Pearly Gates.
I use EMG pickups in mine, not sure if that route it for everyone though since it's a bit of an odd mix, but the bright highs and higher output really punch up the Jag-Stang's output a lot, have to be careful with practice amps since the pickups generate about a volt of electricity and I have fried a few speakers with this setup. It sort of gives it an odd sparkly 80's quality over the top of a very Nirvana-like sound with a ridiculous amount of gain and a nice crunch with the right tweaks to the volume and tone pots.
