Is it possible to make units immune to attacks from for example, queens?
so the queen can spawn broodlings or parasite an unit, but it won't affect the unit. But the unit is not invincible. (staredit)

Sorry, this is not possible. However, for spawn broodling, you could quickly put a new unit where the dead one used to be.

nope, that's not possible.
Just don't provoke the queen, let it ally you or remove the broodling ability from it.

Well.... If you REALLY wanted to, you could constantly center a location on the unit you want protected, and if any queens are nearby, set their energy to 0, it could cause problems though, since it's really annoying to figure out how to set it back properly.

Yeah, because setting the energy back up when they leave means that they get full energy all the time, which is BAD.
A tough predicament.

Hero units should be safe from spawn broodlings if a computer has the queen--I believe its one of those built in starcraft things. Otherwise you could use non-organic ground units which aren't affected by broodlings.

But a lot of mech units are technically brood targets.
All of zerg ground.
All of terran ground, except spider mines, but COME ON.
All of protoss ground except for probes, reavers and archons.

That's not very much to choose from.