Don't throw away your dead light bulbs, they may come in handy one day.
This video will show you how to start a fire using a dead lightbulb. And no electricity. The tricky part is emptying out the insides, but this can be done with sticks and stones, assuming you're in a survival situation and just happen to have a light bulb with you for whatever reason.
The light bulb needs to be filled with water for it to be used as a solar concentration lens so first you must grind away the waterproof ceramic plug. You can do this by rubbing it on a hard, rough, outdoor surface as demonstrated in the video. It's a good idea to wear some protective gloves while doing this too.
Once the ceramic plug has disintegrated you can use a small stick to break through what's left inside the bulb and then empty the remaining contents out.
Now you need to fill the light bulb with some water, it's a good idea to just give it a rinse out a couple of times. Now you have a solar concentration lens, you can use a balloon or something similar over the opening of the light bulb to stop the water from spilling but this isn't completely necessary.
Once you have a target for your solar lens you can start making your fire. In the video, a cigarette butt is used. You can use a whole range of things for your target, some leaves can work well.
Find the smallest possible focal point from your lens and aim it at your target, it should start smoking within a few seconds, you can then transfer this into a larger tinder bundle to make your fire!