"First, he pointed that giant metal rod at me and out came a glass vial, it exploded next to me! Next thing you know, out comes a friggin’ bear! Then, as if that wasn’t bad enough, he sticks it in the ground. It expands and he walks into it to get a snack!" - Xzud, Experimental Arms Dealer.
Atheists and agnostics get a jolt when one or more deities make an appearance, and take a direct interest in things. It is hard to deny the existence of gods when one has met them face to face.