Can a star eat a black hole? I know there are stars much larger than the sun and that we've discovered "small" black holes, so, let's say that the Pistol Star, which is at least 80x the mass of the sun, and the smallest known black hole, XTE J1650-500, around 4x the mass of the sun, collide. Would the pistol star "eat" the black hole, or is there some property that a black hole has that is immune to the star's power? 

I would think that the star would turn the black hole inside out, and like explode or something, but there's also the possibility that once a black hole rips space time the way it does maybe that can't be easily undone. I'm assuming the matter within the black hole isn't going to magically pop back into existence either as it's been broken down into it's most basic parts.
You ask if 


  there some property that a black hole has that is immune to the star's
  power?


The short answer is "yes" -- the property of being a black hole. Assuming the collision is at a reasonably low relative velocity, the black hole would consume most of the mass of the star, so that eventually you would be left with a much bigger black hole and a certain amount of matter and radiation heading away from the site where the collision took place. The details of how long this would take, how much matter and energy would escape and so on will vary depending on the exact structure of the star and the details of the collision.

Essentially you can't disrupt a black hole much by throwing matter into it (if the matter you throw in is VERY dense, like another black hole or a neutron star there will be some temporary disturbance to the event horizon, but it will settle down in a fraction of a second), all it does is absorb the matter and get bigger. Even if the matter is super-hot dense fusing plasma from the centre of giant star. In the course of falling in, the matter gets distorted and heated (much hotter than the interior of even a large star) and sometimes whirled around the black hole, and this can appear as a huge explosion, but in the middle of it, the black hole is sitting there absorbing matter, largely unperturbed.