My go-to digital writing utensil is a full-size Ducky One 2 Cherry MX Brown, with custom keycaps and 50A durometer O-rings. ❤️
I spend so much time typing on a PC, I gladly spent those ~200 USD on a keyboard.
But my go-to pen - my analog writing utensil - is a SureFire EWP-02. Only SureFire product I own, but unlike every single other pen I have ever used, no-brand or yes-brand, the SureFire actually works when I need it to, every time.
I liked it so much, I bought another (shame I did that before I saw the 3-pack gift pack, including the pink one) - got the blue one at home, and the black one, the first I bought, at work. Refills are fortunately easy to get ahold of, even locally, which I checked before buying it.
Had an issue with the clicker a few years back, and SureFire offered to send me a spare, free of charge. Since I knew this would eventually be an issue with my other pen as well (sent them a picure of both pens as proof), I offered to pay for some more clickers, since they were going to send a parcel to me anyway, and some or all of the shipping cost too. I didn't get any more replies, but a week and a half later, a parcel arrived with 6 new clickers.
EDIT:
This reminds me...I sent a final reply back, thanking SureFire support for going way beyond what I expected in terms of service, and promised when or if I could to buy some more of their products. I still haven't done this yet.
/EDIT
I was recently in a meeting including the department head at work (not my boss, but my boss' boss), and I saw he was trying to make some notes. But his pen didn't work at all, so I silently handed him the SureFire across the table. He looked at the pen, looked at me, nodded and mouthed a silent "thank you", and used it to make his notes.
...Then I saw him put the pen in his chest pocket, where he had kept his own pen. And mentally I was like "you take out that pen now, or I take you out the window now". I do not remember what the rest of the meeting was about, because I only focused on keeping track of where my pen was.
When the meeting ended a bit later and we all stood up, I gently asked the guy to have my pen back, and pointed at his shirt pocket. And then I knew it had not been intentional, because his face became a mask of sheer terror. He glanced at the table where his own pen still was, and started apologizing to me profusely, and made sure everyone else nearby heard he had made an unintentional mistake as he handed me back my SureFire pen from his pocket. I equally made a point back to ensure him and those who heard that such mistakes happen and it was not a big deal.
Isn't even the first time this has happened. Almost every time I bring it to a new place or I let someone else borrow either of the SureFire pens, whichever I have with me at the time, for some reason or another, I almost lose it.
As for the Fisher Space Pen, the Russians actually did it better when they brought a pencil instead. And as supposedly for working underwater, I don't know of any waterproof paper yet.