Asklemmy

Obsidian and VLC.

Pipewire

Ddrescue

Hard to beat for working with dying drives, although it's a bit tricky to get it to just do used data areas instead of the whole drive.

Since you're saying "pieces of software" and not specifically apps I will mention Node.js, the programming framework for javascript apps that run outside of a browser. You can develop websites and services or standalone apps that just run locally. There's a whole universe of free packages people have created for it.

Notepad++ is also great for searching text strings in many documents and collating the results in a single window.

It's a niche thing, but if you play electric guitar and need a virtual amplifier and effects, you'll like Guitarix very much. Just thinking that is a community project blows me away every time

WinDirStat, Notepad++, Greenshot and Filelocator pro lite (aka agent ransack) are my default programs to install on windows machines.

Krita

For keeping track of investments I recommend: Portfolio Performance

https://www.portfolio-performance.info/en/

Takes maybe 10min to learn the basics in the beginning, but it's worth it. Nice robust open source software which does its job flawless.

OnShape for designing 3d objects. I've been using it for 3 or 4 years, after outgrowing TinkerCad (which is also good and beginner-friendly, but limited). It's an online app, nothing to download or install. The free version is fast and full-featured. The only difference between it and the paid version is that in the free version your designs are all public. So if I were doing 3d design for business I probably would use software that resides on my computer. But as a hobbyist IDGAF.

Ninite.com

kate is similar to npp.

EarTrumpet, Borderless Gaming, ClickMonitorDDC, Lenovo Legion Toolkit, FanControl, PEACE + Equalizer APO, Everything, TreeSize

Actual - Accounting/budgeting/etc

Wrote up a python script or three to handle parsing my bank CSV export files into an actually usable form, with automatic categorization, and so now I just do a periodic export and sync, and have all my financial records all in one place with some nice visualization, categorization, and budgeting features from Actual. It saves everything to a local sqlite db, so I can always jump ship to a different system if needed, and also itself provides a CSV export option.

10/10 software, would recommend

X-Inkscape for vector graphics. It has a ton of functionality out of the box and it can be enhanced by coding your own plugins. I love it

ZoomIt - Sysinternals at https://learn.microsoft.com/en-us/sysinternals/downloads/zoomit

That small free application will notably allow you to press a key combination to "zoom in and out" on your screen and "draw" on your screen with your mouse. When presenting something using an external monitor, you can use that tool to draw attention to specific things or zoom in on tiny details when people are having issues seeing something. The link also show a small preview of what the application does.

LibreELEC, which is a minimalist 'Just enough OS' Linux distribution for running Kodi. You can use it to turn almost any (mini) pc into a full fledged media center.