My personal top picks of the pedal world.
Maestro Fuzz Tone
While the Maestro Fuzz Tone might not be the very first fuzz, it was the first major commercial fuzz. It has an unusual circuit among fuzzes. It squashes so hard it can even have a pseudo volume swell effect.
Sola Sound Tone Bender/Dallas Arbiter Fuzz Face
I love the Tone Bender story! There's so many angles to it. I can't do even a summary justice here. Read the story at kitrae's site. It's epic.
Vox Wah
Still the most popular guitar effect of all time.
Octavia/Octavio
Roger Mayer and Jimi Hendrix introduce octave up fuzz to the world on March 17, 1967 with the release of "Purple Haze." This sound is something new.
Shin-Ei/Univox/Korg Superfuzz/Univibe
Fumio Mieda, all the way over in Japan, hears this new sound from Mayer and Hendrix and creates his own version of octave fuzz. This design, perhaps originally released under the Honey brand as a "Baby Crying" fuzz realizes the full wave rectification to produce an octave effect with transistors instead of the Octavia's transformer. It is unlikely Fumio knew what was used by Hendrix. He probably just invented the circuit to realize the sounds he was hearing. Unichord of New York picks up this Japanese product line and sells it as the Superfuzz. The schematic is pasted right inside the pedal for anyone to copy. And copy they do! The Fender Blender, Ampeg Scrambler, Foxx Tone Machine, etc all are likely inspired by the Superfuzz.
But Fumio didn't just make fuzz - he made a Leslie speaker simulator (another nod to Hendrix) that became well known, even used by Hendrix, as the Univibe. Both fuzz and phaser were combined in the Honey Psychedelic Machine, a combo effect unit that looks like a small amp head.
EMS Hi-Fli/Electro Harmonix Small Stone/Electro Harmonix Micro Synthesizer
David Cockerell made EMS work. Peter Z. needed to realize ideas he had, and Cockerell made them actually happen. In addition to making synthesizers for EMS, David made a multi effect unit for guitarists called the EMS Hi-Fli. This unit is pretty rare and pretty awesome. Its greatest claim to fame is its use on Dark Side of the Moon. David felt that EMS synthesizers were done when the Mini Korg came out (designed by Superfuzz designer Fumio Mieda... small world!) so he left EMS and England and came over to New York City. In New York, David found Mike Matthews of Electro Harmonix and gave him a phaser design straight from the Hi-Fli. This is the Electro Harmonix Small Stone. Later, a stripped down version of the Hi-Fli appeared as the Electro Harmonix Micro Synthesizer. David also designed the Electro Harmonix digital delays, and he and Mike sold Akai on digital delay/sampling technology in the '80s... this led to David designing the hardware for Akai including the MPC series. David still designs for Electro Harmonix. He recently told the engineers there that his favorite design to date is the Ravish Sitar.
Big Muff Pi