[Schroedingersat]

If your object is roughly the size of a wavelength or less, it can siphon off power that would be a few wavelengths away.

So a bacterium might be able to annoy their neighbor. But that's about it.

If the sun was in some kind of equilibrium with stuff around it (ie. There was a big mirror acting kinda analogously to a ground plane) you could effectively cast a shadow much bigger than yourself.

But that's about it. Visible light is very small.