Gunpowder is a dust just like redstone, but why can't you place gunpowder down to act like a fuse. Forsay redstone could be used to do that, but gunpowder could maybe burn nearby blocks when ignited. It would also be more delayed and be more realistic rather than it being ignited instantly. I know you can use repeaters, but they could blow up in the process. It would look like a greyish stone color of redstone when placed down. You can also ignite it so when mobs walk over it, they burn. It can also work on players, but if a mob or player has boots on, their feet will be protected. I think that this could be useful, but also bring another use for gunpowder for the game; expecially when you have killed a lot of creepers in your days of Minecraft.