Walk Through Certain Colliders?

Okay so I have done some research and cannot find anything on this topic. So here is my question. I want my player to be able to walk through certain colliders. For example when my player kills an enemy, the enemy falls apart, each part contains a box/sphere collider and a rigidbody. However since my player has a collider if any of these parts land in front of him, he walks over them. So how can I make it so that objects fall, don't sink through the ground, but can still be walked through? Sorry if this sounds confusing I'm just trying to determine how I should go about this. Any help is greatly appreciated!

Thanks!