Linux

Noto Sans for sans-serif text (and the OS)
It's legible, standard-looking and support about every writing system in the world. You can install it on Debian using # apt install fonts-noto, some others like -cjk and -extra help with the "supports about every writing system in the world"-aspect.

Merriweather for the serif font fallback for the browser, as well as TTRPG campaign printouts
It's very legible, and looks quite sexy for a serif font. There's no package for it currently (although AUR and Nix users might have better luck), it has to be downloaded from Google Fonts

JetBrains Mono for the terminal TUI's
It looks a bit playful, like lego-letters, is legible and supports about every writing system in the world. # apt install fonts-jetbrains-mono.

Although I use...

Verdana for source code
It differentiates every character well and leaves enough space to easily recognise special characters such as brackets. And I don't believe monospace fonts are more legible. It's included in ttf-mscorefonts-installer but the font is not open-source.

Inter for desktop and the nerd-font variant of JetBrainMono for Terminal.

I've been enjoying Fira Sans and Fira Mono for far too long: https://mozilla.github.io/Fira/

Please don't hate me but for desktop I use Segoe UI. After years of using it everything else looks just kinda off and cheap to me. Similar to when folder icons are not yellow

Iosevka.

I've been a fan of IBM Plex for a while now.

Ubuntu font. Idk why but I like it.

Since basically forever I use DejaVu Sans for UI elements and DejaVu Mono for the terminal.

Protomolecule for that scifi feel

I've been using Source Code Pro for a while now. Might not be the best, but it does the job for me.

For desktop, I've liked Lato, Source Sans Pro, and Inter to name three.

For terminal, I used Iosevka's customizer to create a gorgeous Fira Mono-like variant that I call Iosevka Firesque:

[buildPlans.IosevkaFiresque]
family = "Iosevka Firesque"
spacing = "term"
serifs = "sans"
noCvSs = true
exportGlyphNames = false

  [buildPlans.IosevkaFiresque.variants]
  inherits = "ss05"

    [buildPlans.IosevkaFiresque.variants.design]
    capital-g = "toothless-corner-serifless-hooked"
    capital-q = "crossing-baseline"
    g = "single-storey-serifed"
    long-s = "bent-hook-tailed"
    cyrl-a = "single-storey-earless-corner-serifed"
    cyrl-ve = "standard-interrupted-serifless"
    cyrl-capital-ze = "unilateral-serifed"
    cyrl-ze = "unilateral-serifed"
    cyrl-capital-en = "top-left-bottom-right-serifed"
    cyrl-en = "top-left-bottom-right-serifed"
    cyrl-capital-er = "open-serifless"
    cyrl-er = "earless-corner-serifless"
    cyrl-capital-u = "cursive-flat-hook-serifless"
    cyrl-u = "curly-motion-serifed"
    cyrl-capital-e = "unilateral-bottom-serifed"
    cyrl-e = "unilateral-bottom-serifed"
    brace = "straight"
    ampersand = "upper-open"
    at = "threefold"
    cent = "open"

For terminal/editor I went through CodingFont and ended up on Noto Sans Mono. Before that I used Source Code Pro for years. Both patched for nerd fonts, obviously.

Lexend Deca for me. A mix of a dyslexoc-font, Arial and a bit of the roundness of Comic Sans. (Sorry, probably bad examples, am no font nerd)

Hack nerd font is my go to for terminal use.

For sans-serif, I use Mona Sans. For monospace, I use Monaspace. I think it's a good-looking combination.

any with a dotted zero, extra points for italic.

Gohu Font Nerd is a nice small bitmap font I'm fond of. Only issue is the size for high DPI monitors, but the JetBrainsMono nerd font is a nice vector font that's easy on the eyes (quite stereotypical/cliché, but that's for a reason).

U001 is my main system font as a clone of Univers. Monospace is Berkeley Mono—it might be paid/proprietary but boy does it look nice & was an upgrade from several years with Iosevka. JuliaMono is its fallback though since I use Unicode with frequency & Berkeley doesn’t cover all the symbols I use.

The important part is if you care anything about your fonts, you won’t destroy them by patching in that uncurated hodgepodge called “Nerd Fonts” clobbering used symbols or the wrought-with-false-positive “coding ligatures” which is not how ligatures are supposed to be used but programmers refuse to demand Unicode support in their languages to fix the problem.

Personally, whatever is default.

I know that may sound weird, but I'm a huge fan of sane defaults that I don't even notice are there.

I find comic sans mono actually looks surprisingly nice for coding and terminal.

I like Maple Mono https://github.com/subframe7536/maple-font

Code new roman! It's so cosy, and readable. I am a sucker for fonts with the cursive styled 'a'

I like Delugia for any monospace needs. It's a nerdfont, and it's nicely readable without looking too chunky.

I love Eurostile Regular. Git it at https://freefonts.co/fonts/eurostile-regular

I always end up with SF Pro Display for my desktop. For terminal I’m happy with several mentioned here.

I use M+ Fonts for most of my stuff.

Fantasque

I've been using Fantasque sans mono for a bunch of years now.

i want serifs. I use Go Mono for monospaced text. i've yet to find a good proportional slab serif font to match though.

Lato, League Spartan, League Gothic are my three most used fonts by a wide margin. Lato and its variety of weights for most things, League when I am doing design work and need a cleaner title or header.

Lately ive been weirdly taken with TT2020 Style G, which is an odd name for a no-name font that replicates an old imperfect typewriter. For whatever reason, switching my writing software to that (Manuscript) suddenly fired up my writing flow.