Camping, trekking, backpacking, BBQ'n. Need to make a fire and you only have your pocket knife? Well, you could:
1. Strike the blade against a sharp hard rock and catch the spark in specially foraged tinder, then nurse that spark into a coal.
2. You could also use the knife to whittle and bow drill and start a fire with friction.
3. The easiest option it to be prepared with the right pocket knife.
If you would like to learn more about starting a fire in the wilderness, this site offers a very comprehensive report on just about every way.