The Flaming Sphere spell states that "It ignites flammable substances it touches and illuminates the same area as a torch would."
So if a Flaming Sphere rolled into or through a square that had a Fuse Grenade in it, would the sphere ignite the grenade's fuse? (my gut reaction: yes) Furthermore, if a character in the same square as a Flaming Sphere were to pull out a Fuse Grenade, would the grenade _automatically_ light, or would you still make the character spend a move action to light the fuse? (I want to say it's a free lit fuse, but I'm biased)
FYI, I'm running the Ironfang Invasion campaign (first time as DM in pathfinder), and I'm dying to have my hobgoblins use the Sting Grenade, but it just takes too long to pull one out, light it, and throw it to make it worthwhile. However, the party has a character who keeps using flaming spheres to make my life difficult and they're going to be going up against a group of hobgoblins for a rematch fight (at Camp Redjaw - party had to withdraw from the first assault), so I figured it wouldn't be too cheesy for the hobs to be waiting around with sting grenades at the ready - they've already seen the flaming sphere once, so they'll prep for it for the second encounter.
PS - for extra fun, what if you had a hobgoblin wearing a bandolier with 3 fuse grenades in it, and it gets hit by a flaming sphere - all three fuses lit? Heh heh heh...