For a compass, I use the Silva Guide: liquid filled, mirror sighted and less than an ounce. If you work with magnetic bearings only, there is seldom a need to correct for declination.
For starting fires, I presume you are talking about "that one fire that absolutely, positively, must be lit or you will die". For that purpose, I always take along a half-ounce, vacuum-sealed packet of lifeboat matches and several wax impregnated cardboard and sawdust fire starters similar to the old "C-ration" heaters used during WW-II and Korea. Lifeboat matches produce a flame, not sparks, and they will burn under water (literally). The fire starters will burn about five minutes individually and 20 minutes collectively.
I guess I have never seen much point in messing around with a derivative of flint, steel and tinder when what you need is the moral equivalent of a cup of kerosene and a good match (or a thermite grenade). Sure, the sparkers can give you the feeling that you are an accomplished woods-person but, for me, when my life may be at stake, I am more than willing to forgo that pleasure.