James "the Amazing" Randi is the nation's foremost debunker of silliness. He has a standing offer of $1 million to anyone who can prove they have any sort of paranormal power. He has handled all sorts of takers, of course, from the silly to the sublime.
To give you an idea of what this challenge is like, his group has posted a four-part video series on YouTube where they test a nice woman named Rosemary Hunter, who claims she can make people, um, pee on command. Here's Part 1:
She seems very sincere, and I am sure she believes she can do what she can do. No doubt she got involved in a set of self-confirming circumstances where she really began to believe she had this power (no doubt reinforced by remembering the hits and forgetting the misses). You can see that the testing procedure was set up well, and she had no problems with it. And the results, well, you can see for yourself. But it's a total of 26 minutes, so you might want to take a potty break first... however the test winds up going.