QOTW: Which free PC software should everyone be using?

[AlSomething]

Chrome
CCleaner
Onenote
CPU-Z
Steam
Spotify
Skype
Nitro Reader
Oracle VM
inSSIDer
BBC iplayer
Kodi

[Ferral]

Oracle VM as it can run XP and 98SE etc which is great if you are into your retro stuff as a lot of utilities are old DOS based or XP 32 Bit, as an example if you have the UltraSatan for the Atari ST Vista and above will only see 1 partition on an SD card, however you can hack a driver on XP 32 Bit which makes the machine think it is a partitioned external hard drive making transfer of files to the ST much easier.

F.Lux is another great little program, I got it after a recommendation from either another forum user or news story here. Basically it tones white balance down on your screen after sunset which in turn causes less eyestrain

7Zip is a great utility which has high compression and decompression and supports all zip formats (rar etc)

Picasa from Google is great for tidying up & manipulating photos and sending them off to your Google storage.

[peterb]

Linux

[humoos]

Forget Notepad++. Sublime Text 3 is where it's at.

[OilSheikh]

VLC Media player
WinRAR
Avast free antivirus
uTorrent

How did you guys forget these ?

[PuremasterZ]

Inkscape and Blender.

[Brian224]

Yet another one for Notepad++, but also Netbeans (yes, I still use Java, no it isn't malware). Microchip's MPLAB is pretty handy too.

[SteveWilliams]

Linux

Absolutely this.

[g8ina]

CCleaner
Foxit
Faststone Resizer
MKVToolNix
MusicBee

[andrewuk]

AviDemux - useful video editor (and not just for avi!)
Notepad++ - essential
paint.net - good free image editor
FreeFileSync - I use this to backup and sync my documents, favourites etc on multiple devices
KeePass - keep your passwords safe
Filezilla
PuTTY
Oracle VirtualBOX
Bulk Rename Utility
Peazip
MKVToolNix - a godsend if you do a lot of video editing and need to merge video/soundtracks etc
plex/kodi/vlc

[cheesemp]

Notepad++
Chrome
7zip
Teamviewer

[this_is_gav]

Forget Notepad++. Sublime Text 3 is where it's at.

It's also very much not free.

[DDY]

Foobar2000 - An incredibly capable and flexible audio player.

SoftEther VPN Server - Multi-platform and multi-protocol VPN server with much GUI goodness, most importantly for me it's fairly noob friendly.

[3s-gtech]

Foxit. Got the Enterprise version deployed on ~1000 PCs at work.
7-Zip
WinSCP
VirtualBox
Winamp (still rocks for managing old iPods)
GIMP
Inkscape
VLC

Plus hundreds of great apps at work like NTFSFix and Wisesoft Account Management.

[failquail]

Hard to list them all really, but ones that come to mind initially:

openhardwaremonitor - if you have dual monitors, open the show gadget option and drag it to your second monitor, you can then easily monitor what your hardware is doing when doing other things
CPU-Z
GPU-Z
Notepad++
Irfanview
dup-detector If you're disorganised with image downloads or camera downloads, this is a great way to remove duplicate files...
VLC - The default win10 video player is probably the best microsoft have ever managed and often can work better hardware-acceleration-wise. But VLC has the compatibility record win hands down, if any program struggles playing a video file, try VLC...

I'll add to this post if i remember others

[EndlessWaves]

Let's not start listing all the free software on our computers, lesser known suggestions is the QOTW.

I tried a lot of archivers lately after I couldn't get IZArc without a dubious installer. While 7-zip is brilliant for creating files I felt it's generally interface left something to be desired. I found the best setup was to use the fast and neat Bandizip for general extracting duties but to leave the Add to archive... context menu option from 7-zip for when I needed to create an archive.