I’m not sure if this fills the requirement of iconic, but John Mayer uses the POG on In Repair. There’s a video called “One song, one day” where they show how the track was written and recorded.

Also, I don’t remember what tracks it’s used on, but I remember listening to an interview with John Frusciante on musicradar.com where he says that he used the English Muff’n on The Empyrean.

Nice links, thanks. I’ll especially be taking a closer look at the Small Stone ones.

By the way, for posting a link with a space in it, it works if you wrap URL-tags around the link, like so:
http://www.student.ru.nl/r.kerkhof/Taas/Mods/Big Muff.htm

Press the quote button next to my post if you want to see what it looks like.

Alternatively you can do the same by pressing the button in the row of buttons over the textfield where you write posts.