I'm interested in what applications people use, maybe I can discover some better alternatives.

Music: Spotify for streaming, Dopamine for local music.

Cloud: OneDrive. As a student, I get 1 TB of space for free.

Email: Mailspring, though I'm eyeing eM Client as an alternative right now.

Text Processors: Mostly VS Code with LaTeX, but I do sometimes use good old MS Office.

Code: VS Code again, and also IntelliJ IDEA and CLion for the respective languages. VS Code for anything that isn't C or Java related. I'm also watching the development of Oni Vim 2.

PDF: On my laptop with a touch display, I use Drawboard. On my PC at home I use Nitro PDF.

Browser: Firefox, ever since the quantum update it's nice and snappy. Though maybe I'd switch to Vivaldi when they add Sync at some point.

I have discovered hackmd.io a few months ago and started digitalizing my massive mess of handwritten nodes together with all the terrible notepad/word mixed notes into one big personal "wiki" of knowledge. But I ran into a problem. HackMd can only handle ~50k characters before starting to lag and 100k characters is the limit per note, this doesn't even fit my one summary/tips note on one programming language. Do you know any alternatives? I really like markdown, since all of the notes look clean and organized, I can insert pictures and link to websites easily, but also love to work with them online, since I have to switch between 3 computers between university, home and my laptop.

What are some apps that you use that aren't particularly well known? Let's help each other discover some interesting new tools!

lichess - best chess app out there IMO. Completely free and open source, has daily puzzles, and a pretty active pool of users to play against!
Syncthing - file syncing tool that works with just about any operating system (although I don't think it works with iOS). I use it to take notes and write lyrics/my journal and sync them back to my linux laptop.
Untappd - social media app for tracking craft beers that you drink. I've only just started using it, since I was on holiday and wanted to keep a note of the ales I was drinking. It's a free app, but supported by ads. I believe there's a paid tier, but the free version works well enough, and it's useful for encouraging me and my friends to try new beers when we're out and about.
WK - Japanese flashcard app, which is technically a front-end for the wanikani service. As you learn new radicals, characters, and vocabulary, it serves them back up to you after a certain length of time. If you remember it, it'll wait longer next time, and if you don't get it right, it brings it back to the top of the pile.