I originally used zooms of various lengths. About 16 months ago, I bought a very nice Zeiss 24 fast prime on my NEX 5N. I quickly discovered that I didn't want to use any other lenses. After a while, I started seeing the world with my Zeiss 24 in mind and I don't even see the shots I am missing by not having a 200 lens or a fisheye or whatever; I see shots all around for the lens I am using. When I upgraded to the Canon 6D, I soon got the Sigma 35, which offers the same perspective as the Zeiss 24 on the cropped sensor. I have taken international trips (e.g., even one to Africa) with this focal length. Even though I had other lenses, I was content to shoot at 35 for my photography (I used a long zoom for 2 hours on a whale watching boat ride and that was it). To me, 35mm is extremely versatile. I have no regrets about selling my 24-105 since it wouldn't handle the low light shooting I do. Perhaps my biggest regret is buying a 50/1.2L since it sits around too often.
I do think about adding a 100/2.8L, but that would just be for some macro work; otherwise, 35 covers it all for me night and day. I shoot far too often inside where the f/1.4 comes into play and I won't get that with any decent zooms. In 16 months, I've never had a situation where 35 (or my Zeiss 24) was not wide enough for my family shots. And, around the house I can also zoom with my feet for family shots. I am not suggesting that my needs are the same as the OP; I am just noting that I find the 35 focal length to be perfect for nearly every shot I want.