What if this planet existed and you fell in? Let's take a look at that and see.
I'll spare listing all the reasons why a planet like this can't exist and wouldn't last long if it did; those are no fun. So instead, let's say this planet does, for some reason, exist in some galaxy far far away and it's made of something strong enough that it'll be around for the long haul (So that's where all the adamantium went!). As stated elsewhere, the shell theorem says that the gravity inside this big, metal, hollow sphere should drop to zero. This happens because the distribution of matter on all sides has a net canceling effect on the gravitational force felt by anything inside the shell. But now we're assuming there's absolutely nothing inside the planet shell. Is this really realistic? (that is, is it realistic for our unrealistic plant-shell scenario? Because if it must be unrealistic, it should be at least realistically unrealistic. I think that's a realistic requirement).
So here you are, strolling around on this planet shell because, as you say, that's a neato-burrito find (that's the technical term, I believe). Is there air? Or are you in a spacesuit? If there's air, we have a problem. You said this shell has a hole you inevitably fall through. How big is this hole? 2 meters across? (Why, that's no bigger than a womp rat). That means the atmosphere is linked to the vacuum inside the shell. I'll give you two guesses what happens next; it isn't pretty. The pressure from the atmosphere would rapidly push air into the interior of the shell using the hole as a massive Venturi tube. Not to mention the decreasing gravity on the way down would continue to increase the speed of the air molecules and, thus, pull air from the atmosphere faster. I'm no doctor, but I can tell you that would make a pretty big shockwave through the atmosphere. You probably wouldn't live through it (pfft! Not with THAT attitude!). If you did, what you'd find after an equilibrium is reached is that now the shell isn't empty. As such, not only would you have air resistance to deal with when you fall through the hole, but there would be a net gravitational effect inside the shell due to the mass of air it contains (albeit, not nearly as strong as the gravity outside the shell). The result? You aren't coming back out. You'll oscillate a bit and come to rest at the center of the sphere. Or you'll be annihilated when the atmosphere rushed into the shell, but let's not dwell on unpleasant things.
Okay, you say, what if I were in a spacesuit and there was no atmosphere? Phew. I've got just one problem now. You're now in a galaxy far far away, on a giant metal sphere about the size of a small moon that's mostly hollow inside and has a 2 metre shaft that leads directly to its core. You should expect regular gravity everywhere inside because, contrary to what the shell theorem says in this case, I'm fairly certain the Death Star had artificial gravity generators.