According to EHX official website John used/uses a EHX HOG.

"He runs two pedalboards, one for acoustic and one for electric. The acoustic board consists of an Ernie Ball volume pedal, Boss FRV-1 reverb, TU-2 tuner and a Radial Tonebone PZ-Pre acoustic preamp. Electric-wise, there’s a Menatone King of the Britains, Electro-Harmonix HOG, Digitech Jamman, Electro-Harmonix Deluxe Memory Man and MXR 10-Band Graphic EQ, all powered by a Dunlop DC Brick. It’s an impressive selection and one that ensures Cornell’s acoustic shows are so much more than just, well, acoustic."

The image of Jamie Cook's pedalboard from the Favourite Worst Nightmare tour shows an EHX HOG Foot Controller and an M-Audio EX-P Expression Pedal, which are used to control the Electro-Harmonix HOG Harmonic Octave Generator. Although the HOG unit itself is not visible, its presence is implied by these controllers, suggesting it is likely placed under the raised section of the pedalboard. The distinctive sound of the HOG can be heard on several tracks from the Favourite Worst Nightmare album and its b-sides, notably in the song "What If You Were Right The First Time?" at 1:32, where Jamie Cook utilises the expression pedal to bend the notes and add a high octave effect during the breakdown. It is used more subtly on other songs, such as 'Do Me a Favour' and 'This House is a Circus'.

Kevin Cochran takes us behind the scenes of Radiohead's gear when they came through Austin, TX in this article from Austin City Limits.

Coxon's playing makes significant use of effects pedals such as distortion, delay (a significant example being "Essex Dogs") and flange (as heard in the pre-chorus of Girls & Boys). He uses a custom made Mike Hill pedalboard which over the years has included: Akai Headrush E2, Boss BF-2 Flanger, Boss CS-3 Compressor/Sustainer, Boss DD-3 Digital Delay, Boss DM-2 Analogue Delay, Boss OD-3, Boss NS-2 Noise Suppressor, Boss PN-2 Tremolo/Pan, Boss RV-5 Digital Reverb, Boss TR-2 Tremolo, Boss TU-2 Tuner, Boss VB-2 Vibrato, DOD Punkifier, Electro-Harmonix HOG, Electro-Harmonix Holy Grail, Line 6 FM4 Filter Modeller, ProCo RAT, Shin-Ei FY-2 Companion Fuzz, T-Rex Mudhoney Distortion. (Wikipedia)

In the Funksheet article "Wes Borland Gear 2009," photos reveal that Wes Borland uses the Electro-Harmonix HOG Harmonic Octave Generator among other pedals.

In this video, Mike Shinoda is explaining the workings of his HOG Pedal. [@ 0:54] He explains "I love how the HOG changes the whole texture of a beat."

Hann pictured his pedalboard on Instagram where the Electro Harmonix Hog Guitar Synthesizer can be seen. Hann also has the HOG footswitch accessory on his board. The HOG is prominent in Hann's parts in "M.O.N.E.Y."

In this source by Premier Guitar the Electro-Harmonix HOG is listed as part of his studio gear.

Used in his Metal Machine Trio tour, barely visible on the top-right corner. Picture © Pete Cornish: http://www.petecornish.co.uk/GreySeries.html.

Richie is complete artist but I want to see him play some songs with blues harmonica sound. This Eletric harmonix's pedal "hog" makes emulates "Blues Harmonica". He should try!

Sold for charity on Moby's official Reverb shop.