1) Electro-Harmonix Big Muff Pi.
Reactions to this news will be split into groans and shouts of joy. The EHX Big Muff is nearly ubiquitous, it's the most popular fuzz pedal in the world, and is the first pedal many people picture when they think of fuzz.
But the thick and saturated fuzz tone doesn't suit everybody's tastes, and EHX recognises that, hence the sister models they have introduced.
EHX was making Muff Fuzz back in the late 60s, so it's certainly a classic, and even when the company fell on hard times and went out of business in the 80s, the pedal was kept alive by cloners.
It's probably the affordability and the genius/cheeky naming of the pedal that combine to make it so well-known and so commonly-used among guitarists of all levels and abilities.
Depeche Mode even named a song after it, and of course, the pedal is used on the song.
Songs that used the EHX Big Muff: