As great a fan of Richter as I am, I’m not so deluded as to think he was particularly skilled with pianissimo. Even Gilels, though much better, hardly compares to some of the other greats.
In my opinion, two such masters of pianissimo are Gieseking and Hofmann.
There are many more, including Barere, Friedman, Fiorentino etc, but those are two that stand out for me.
Who are your favourites?
I think Gilels has some wonderful pianissimo moments though, like in the Bach-Siloti Prelude.
uh, i’d actually say Richter right off the top of my head. in one or two of his 4th ballade recordings, the pianissimo chords right before the coda are the most beautiful and velvety i’ve heard. also in some of his WTC playing, the pianissimo and expression therein is fairly superb.
i’ll have to think more on it for others
Well there’s no doubt Richter has his moments, but I’m thinking of pianists for whom pianissimo is a central part of their style.
Ginzburg and Curzon are the ones I’d think of, and Richter actually (D 894 for eg). I’m not a big fan of Curzon generally, but I remember being impressed by the different gradations of pianissimo he was able to achieve.
Uchida. I don’t care what you guys think of her, she has sooo many soft shades, it’s ridiculous!
even da Ho was jealous of Gieseking’s ppp.
Gieseking - his Debussy is always coloured so perfectly well. Wish I had a recording of him playing his R. Strauss Ständchen transcription though…
Geza Anda maybe, he’s really impressed me on a few occasions
Andreas Luchessini
I for one was impressed by trumofo’s pppp.
i’ve never heard any of his playing. is it any good?
Moiseiwitsch.
He makes up for in sheer chops what he sorely lacks in personality.
This may be a suprising one, I was suprised when I heard him. I went to Demidenko in Vancouver when I was over there. He played a Mozart Fantasy which had some beautiful colouring in it.
Then he played the 24 Chopin Preludes in the 2nd half. When he played the famous C minor. In the 2nd half of the prelude, he played so quietly, I thought he will never be able to play any quieter when Chopin asks for it still quieter. He managed it though and all with perfect control and nicely voiced etc. I was quite in awe. Maybe it was partly due to the venue and also that he was playing a Fazioli, but it really was something. I always imagined him to be piano basher.
Another pianist whose ppp astonishes me is Glenn Gould, particularly in the Art of Fugue and the Brahms Ballades etc.
True, the Brahms Intermezzi especially.
Ban alert 
I’ll agree, and in Papa’s D Minor concerto
Surprised no one has mentioned ABM.