Fire charges can, unlike Flint & Steel, be used on non-solid, non-flammable top-surfaces. I have tested it on the following:

• Stone-type slabs/stairs/walls (not upside down)
• Nether brick fences, iron bars and glass panes
• Gold/iron/stone pressure plates and stone buttons
• Levers, torches, end rods, turtle eggs, sea pickles and flower pots
• Soulsand, grass paths, farmland and (stacked) snow layers
• Cactus, grindstones, anvils, bells and stone cutters

Upon using the Fire Charge on the top surface of these blocks, a fire block will be briefly seen before flickering out. The Fire Charge is, unless in Creative mode, consumed.

To replicate:
1. Obtain a Fire Charge and Flint & Steel, and place any of the above mentioned blocks.
2. Use (Right-Click) the Fire Charge on the top surface of the block. (In the case of some blocks, this may require you to Shift+Right-Click.) Do this in Survival mode.
3. Observe that a fire is indeed placed, and that the Fire Charge is consumed.
4. Repeat step 2. with the Flint & Steel. Observe that nothing happens.

It should be noted, that the fire charge can also be placed in Creative, but does not consume the fire charge.