I have recently done a wilderness survival merit badge campout with my scout troop, and we tested some. I have lit the following with a spark:

cotton (w/vaseline)
Wetfire (must not be exposed to air for too long)
Crumbled Weber grill starters
Esbit cubes crumbled
dry grass (with a blast match)
paper (with a blast match)
alcohol
cedar bark
pine needles (rubbed together to make finer fibers)

I also tried another type of grill starter, and I am trying to track down some more as I can't remember the name and it is not on the small packages. I have had them for several years, and they are packaged in a nice waterproof plastic. You are supposed to light the package with a match. I tore the open and crumbled the stuff inside and it ignited with a spark.