Sidivan
Fractal Fanatic
These are actually pretty cool. Interestingly, the "bonus" one with the 18k hz was actually very audible to me. This is strange because I had my hearing tested last year and I have mild-moderate hearing loss at 8k (didn't test above that) so I didn't expect to hear a tone that supposedly only people under 20yrs old can hear. My wife, on the other hand, cannot hear it.
Top 10 Incredible Sound Illusions
Top 10 Incredible Sound Illusions