Mostly Leuchtturm, mainly because I really like their notebooks and the variety of them that are available. The paper is fine, but not like tomoe or anything like that. I mostly write at work during meetings etc., so the notebook is equally important to me. Open to other suggestions though!
Unlined A5 Clairefontaine for journals, Kokuyo B5 Campus Notebooks for study, and whatever is available for loose-leaf or temporary notes (I do have a lined A4 Rhodia pad in case I need to write something good on a single sheet, but I never do).
Perhaps if I got into letter-writing I might be more interested in exotic papers, but I'm quite content with using things that are pretty easy to find and shouldn't be disappearing from sale anytime soon. I also don't use anything larger than a western M, so I don't need super amazing paper for a lot of my general notes.
My go to is TR 68gsm. I really love CAL too. I have no idea what I will replace them with yet since they both are discontinued. I enjoy Midori MD, but I wish it came in ivory. For notepads I use as scratch pads, I use Rhodia since it's relatively cheap and FP friendly.
That being said, I am in the middle of trying out new paper to replace my go to paper. So far I like Maruman Nmemesoine, but the lack of non-spiral bound notebook variety is a big sticking point. Kokuyo Perpernap is up next. I have high hopes.
I'm told the latest iteration of TR is very close to old TR classic 52gsm. I guess that will be my fallback.
Mostly Clairefontaine and sometimes Leuchtturm1917. I recently bought Rhodia dotpads and dotbooks. I also have an Itoya Oasis light notebook and two Apica notebooks, just for trying them.
Anything but Moleskine because that bleeds and feathers heavily. Leuchtturm1917 adnd Clairefontaine daily, and a Cornell A5 weekly diary that seems to take virtually any ink despite being 'only' 70gsm. I veer towards 90gsm usually.
Oxford Optik Paper 90gsm - it does wonders for me because here it is cheap, widely available at any stationery-related shop and comes in a variety of formats (spiral, bound, loose-leaf, planners, etc). The value/price in the Euro zone is unmatched IMHO.
Clairefontaine A5 bound notebooks, specifically the My Essential line --- designed to answer Leuchtturm bullet journal offers. While a little bit pricey, to me it still beats Leuchtturm1917 in the value/price ratio. They're priced similarly, but the Clairefontaine just offers a better experience with FPs than L1917.
I specifically try to use Navigator 80gsm when I print something and then intend on taking notes with my FPs. Cheap, widely available and a really good value/price ratio.
Tomoe river in my bullet journal, which I got from a pen show.
Another notebook I use is an Apica, and it's probably my favorite paper. It won't show off shimmer and sheen like tomoe river, but it's very smooth and has a fast dry time. For a lot of my inks, I find the long dry time of tomoe river to be inconvenient at times.