Beofrre the wah-wah pedal, there was the Octavia, which "reproduced the input signal one octave higher, and mixes the two sounds with some added fuzz." [Wiki]
After discussion at his friend Jimmy Page's house, and Page's friend British naval electronics engineer and amateur guitarist Roger Mayer invented it. BBC radio (World Service) reported this story last night, but since they don't post radio stories to the internet, there's no BBC link for confirmation. Here's what google says.
The Roger Mayer Wiki page puts the invention shortly after The Kingsmen recorded Louie Louie and before the Kinks wrote You Really Got Me, making this device equal in importace to and generally simultaneous with those two songs.
BBC also said that Mayer invented a lot of new equipment for Bob Marley ca. 1980, and on the radio, it was clear that the instrument had a LOT of new capabilities. It reminded me of crappy 80's dance music.
IMO, this means that, not only did Mayer start the hard rock period, but fifteen years later he killed it. Sometimes engineers don't know their own strength.