I don't see whats so hard here. Part of the reason for invis dropping is game balance. [...] Creating a rock floating above someones head and then letting gravity take over is CLEARLY an intent to attack and cause damage to someone. That would drop your invis just as if you had created a rock and then picked it up and threw it. Same as cutting a rope to drop an anvil. You are targeting someone directly waiting for the correct time to cut the rope. An attack role will be made against your intended target. Sounds like an attack to me.
From this thread: paizo.com - Rules Questions: Flaming Sphere and Invisibility
The wording is ambiguous, and people have been arguing over it for years now. Is this indirect harm, or an attack? It seems to me that sending your big fiery ball of death at someone is a hostile act that would cause the Invis to drop. I would go with Rule Zero on this one.
I'm with Systole and SK on this one. Cutting the rope and directing the sphere both require active intervention on the part of the PC. Summoned creatures have a level of self direction that distinguishes them from the other two examples.
To clarify: My "vote" is that Flaming Sphere (and any other spell effect that requires active direction to cause harm) breaks invisibility.
Thus, an invisible being can open doors, talk, eat, climb stairs, summon monsters and have them attack, cut the ropes holding a rope bridge while enemies are on the bridge, remotely trigger traps, open a portcullis to release attack dogs, and so forth.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.