Assuming were talking wilderness scenarios here, when it comes to on-the-person kit, I usually only carry a fire-steel (on my knife sheath) and some PJ cotton balls. I might also have a mini-BIC in a pocket (especially when camping). If my gear for a given activity doesn't accommodate a belt knife well, it might end up in the pack so I'll usually only have a mini-BIC and maybe the PJ cotton balls (maybe not) on my person.

In my backup/emergency kit which rides in my pack, I'll also have a Spark-Lite & some Tinder-Quik tabs, some UCO storm-proof matches and another mini-BIC. This provides, in my opinion at least, a decent amount of capability/redundancy without much bulk or weight.