Thought I'd make a thread about what "utility" type programs you use, and for recommendations. I'll begin:

Image viewer:
Honeyview

Ebooks:
Calibre & Acrobat Reader

P2P Downloader:
Vuze

System Information:
CPU-Z

Anti-virus/security:
ESET Smart Security

Word processing:
Microsoft Office Home and Student 2016

System temperature:
HWMonitor

Video viewer/codec:
K-Lite Codec Pack

Compression:
WinRar & 7-Zip

Audio files:
Foobar

Internet Browser:
Firefox

Video game client:
GOG Galaxy & Steam

GPU Drivers:
GeForce Experience

I mostly go with simple, focused software, cf. KISS principle.

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Audio/video conversion:
ffmpeg

BitTorrent client:
transmission-daemon and tremc

Chat client:
WeeChat (IRC) and MCabber (XMPP)

E-mail client:
Thunderbird

Game client:
None. Ever. Not even so-called "optional" ones. Not even open-source ones.

Image editor:
ImageMagick and GIMP

Image viewer:
sxiv

Music:
mpd, mpc and ncmpcpp

Movies, podcast, etc.:
mpv

PDF viewer:
katarakt

Software development:
Vim

System information:
Conky

Web browser:
Firefox with uBlock Origin and uMatrix

Uninstaller: Geek Uninstaller
Compression: 7Zip
Image manipulation and editing: GIMP
Bit Torrent: Deluge
Audio Editing: Audacity
Video player: VLC
Chat client: Discord
Email: Outlook (Nothing finer. Tried Thunderbird, but it lacks in functionality I need)
Cooling management: Fan Control
Mouse profile: X-MOUSE
Controller profile: Antimicro, X360X
Emulators: RPCS3, KEGA Fusion, Retroarch, SNES95, Project64, EPSXE, PCSX 2, Citra, Yuzu, BlueStacks
Sys Information: CPU-Z, CoreTemp, WinDirStat Tree directory viewer
GPU management: MSI Afterburner, RivaTuner, NVIDIA GeForce Experience
PDF: Adobe
Browser: Brave with UBlock Origin, NoScript and Privacy Badger
Game Clients: Steam, Galaxy, Origin, Battle.net, Amazon, Epic, XBox, MS Store

Simple math calculation: Python (can enter something like 1 + 1 and get the result)

Text editing: joe

Playing around with JavaScript: node.js (also deno)

Wireless networking: nmtui (NetworkManager client)

Web browser: Firefox (for web sites) and Chromium (for web apps)

Mobile web browser: Fennec F-droid (also, I use F-droid to install software on the phone)

Package manager: apt (I use debian)

x86 emulator/hypervisor: quem (usually with kvm)

Fractal explorer: Godot (with the right shader, the editor can be used to explore certain types of fractals) Same, except that for chat I actually use Chromium running the Discord (or Slack) web app

Web browser: Opera, SeaMonkey and Palemoon, all with UBlock Origin and Rocker gesture (auto scroll) addon's.

Email: SeaMonkey and Opera 12.14 (Presto), both have built-in email clients.

Video player: VLC

Audio player: VLC

Audio Editing software: Audacity, though it is only occasionally used.

Mouse software: Solaar unifying receiver utility.

Image viewer: Eye of Mate.

Emulators: Dosbox, WINE staging. Yes, yes, I know...

Package installer: Synaptic

I have been under the impression that wine-staging no longer brings big improvements compared to the standard development branch of wine, I think I quit using it roughly at the time csmt got merged into a stable wine release.

But maybe I’m missing something and it is still worth running it for some games? Do you use it for some specific features?

Audio player: The "play" command, from the sox package

No, I use it for all Windows games. Though I did upgrade from a very old version of the stable branch (4.03 I think) that I had been using for a few years (without updating) for fear of breaking a specific game I play regularly that worked great. I finally went to the staging branch when I installed a few games that I had (then) recently purchased (from GoG), and the results on the then latest stable update were not good. So decided to stay on the staging branch, and have not found many games that have't worked well. There have been a few that have problems, but they can wait to be tested with future updates...

Image viewer : XnView
PDF & Ebooks : Sumatra PDF
Audio : AIMP4 & Xmplay

Image viewer:
Windows Photo Viewer (restored via the Registry)

Ebooks:
Firefox plugin

P2P Downloader:
Esel (eMule)

System Information:
CPU-Z

Anti-virus/security:
Avira Antivirus (the basic free version)

Word processing:
Open Office Writer, WordPad, Notepad++

System temperature:
HWMonitor

Video viewer/codec:
Mostly Media Player Classic, VLC too

Compression:
7-Zip

Audio files:
foobar2000

Internet Browser:
Firefox

Video game client:
None

GPU Drivers:
None
I ALWAYS manually deinstall and clean up with DDU (Display Driver Uninstaller) and afterwards manually install the latest version

Audio/video conversion:
ffmpeg

Backing up Video:
DVD/BDDecrypter/Avidemux

Backing up Audio:
EAC

BitTorrent client:
µTorrent

Image editing:
GIMP

Audio Editing:
Audacity

This is one I used to use a lot more often: https://www.1-4a.com/rename/ There are also 'better' replacements for it now, like Microsoft's own PowerRename tool, or various open source ones..

I also sometimes use 'streams' from the sysinternals suite (I use tons of parts of the suite now and again) to bulk remove "this is a downloaded file" alternate file stream from a whole path. I used to use it a lot more (especially on the job).

Sumatra's my favorite PDF/ebook viewer I've encountered. (I actually wish it had a direct Linux port...)

I'm an advocate of F/Loss software. You're not going to find me suggesting paid software.

Image Viewer: FEH.

Ebooks: Project Gutenburg.

Anti-Virus/System protection: Laughs! But if I had to suggest, ClamAV/ClamWin. And a healthy dose of SELinux.

Word Processing: Cowlark's WordGrinder.

Video Viewer: Only the one, the only VLC. I haven't thought about codecs in literal decades.

Audio Files: DeadBeef

Compression/Archiving: Xarchiver

File Manager: Thunar.

Version Control: RabbitVCS.

Video Game Client: Lutris

Image Editing: Krita.

Audio Editor: [Pending Replacement] It looks like Tenacity is finally ready.

Graphical conversion: GraphikMagic. It's a fork of ImageMagik.

Bittorrent Client: Qbitorrent.

Browser: Firefox.

Emulators: BizHawk. DOSBOX Staging. [Wine isn't an emulator.]

Image viewer/editor: feh, ImageMagick
Ebooks: xpdf & pandoc
System Information: xosview, top
Anti-virus/security: Emphatically none.
Word processing: xjed (plain text editor) + latex
Video viewer/codec: mplayer
Compression: tar+bz2, even though there are superior methods available (xz, 7z)
Audio files: mpd/mpc, aplay, sox (for editing as well), mplayer
Internet Browser: Firefox+noscript+ublock+tampermonkey
Video game client: Emphatically none.
GPU Drivers: mesa/amdgpu
..
Chat: pidgin, if I absolutely have to. Hate chat.
Email: thunderbird
..
Simple math calculation: calc
Package manager: aptitude (finally got tired of Gentoo after 15 years and switched back to Debian)
..
Emulators, for games: Scummvm, my own patched version of DOSBox. Formerly versions of my own patched Wine (including staging, for the few games that need it), but now that Debian has made it a pain in the ass to maintain such things, I don't play Windows games any more.
..
And, since I spend most of my time in them:
Shell: zsh
Terminal: urxvt
Plain text editing: xjed (as mentioned above)

typically but totally missing the point

Free/Libre Open Source Software. Libre instead of Gratis.

But sure, what point am I missing?