OK, first off, the guy would more than likely be crushed by increasing gravity towards the center. And probably pass out before that. But, for shitz and gigglez, let's just say that the guy falling is invincible. He is superman without the flying and kryptonite weakness. And for all these sick guys who have to get into the incineration and molten lava-_-, lets say it's a hole through a spherical object the size of the earth that has no molten lava. Depending on the aerodynamics of the person falling through the hole, they may reach a speed where, after "bouncing" from one end of the hole to another, they end up in the very center of the hole in a state of suspension. Theoretically, if they happen to have perfect surfaces that would cause no resistance, they may be able to reach a velocity and speed that could "slingshot" them through the other side and into the vast reaches of space. If this where the case, they would continue until they hit something or are smashed into by a passing space rock of some sort.