These aren't just programs I use but programs I suggest people use/switch to. I'll be focusing on the Windows side of things.
Browsers:
• Chrome - People still use other browsers? lol
• Firefox + Safari - To see how websites load on other browsers.
Security:
• Microsoft Security Essentials - It's free and hasn't fucked up yet. Also comes preinstalled with 8.1 and above.
• uBlock Origin [Chrome Extension] - For custom filters and any extra ads not caught in the hosts file. Proven to be a lot better than APB or other alternatives.
• Web of Trust [Chrome Extension] - Community driven safety scoring. If a website is unsafe, it'll tell you.
• Metascan [Website] - For scanning dubious files with multiple AVs.
• MVPS hosts file - System level adblock. A bit too heavy handed but great nonetheless. I suggest this with caution. If you don't know what you're doing, don't do it.
Communication:
• Skype - Everybody fucking uses this piece of shit so I have to use it too.
• Slack - Great team communications software.
• Discord - Great alternative to Skype that's catching on in the gaming world.
• Mumble - Lightweight and low latency VoIP client.
• TeamSpeak 3 - Worse than Mumble at everything else but hierarchy management.
Media:
• foobar2000 - The superior audio player. Has a lot of great features like CUE splitting, ReplayGain, clip prevention, and batch conversion/tagging. It's fast, lightweight and very customizable.
• MPC-HC + madVR - The superior video player combo.
• qBittorrent - So far, the best torrenting client I've used on any platform.
• WinRAR - File compressor that everybody should have installed.
• 7Zip - If you can't buy WinRAR or absolutely hate its nag screen. Basically, free WinRAR alternative.
• WinCDEmu - Better than DAEMON Tools, in my opinion. A bit unnecessary now that image mounting is a part of Windows.
• Spotify - Duh
• Google Play Music - Backs up to 50k songs in 320 MP3 for free.
• Audacity - Even if you don't know jack shit about audio editing, you need this just in case.
Editors:
• Google Docs - Free and quick with great collaboration features.
• Microsoft Office 2016 - For more serious word processing and whatnot.
• SumatraPDF - Superior Adobe Reader alternative since Windows doesn't have a good one built in.
• Notepad++ - The default Notepad is shit and this is a great and easy alternative.
Storage:
• OneDrive - Microsoft's cloud service. Integrated into 8.1 and above.
• Dropbox - Everybody uses it and it's easy to share shit with.
• MEGA - Backup and forget. 50 GBs cloud storage for free. Great for backing up large projects that need to be kept safe.
• Folder Size - Use during maintenance and cleaning by listing every folder's actual size in a nice list.
Gaming:
• Steam - Duh
• GOG - Steam but without DRM.
• Origin + uPlay - Similar to tumors. You have to have them installed to play certain (EA and Ubisoft) games.
Additional:
• Flux - If you don't want to burn your retinas out at night.
• Nirsoft BlueScreenView - Great to see what shitty driver crashed your computer (I'm looking at you, AMD).
• Windows 8.1 or 10 - 7 is a dinosaur and the privacy scare shit now applies to 7 as well so there's no point in having an outdated OS without privacy. If you're really paranoid, switch to Linux.
A good chunk of these apps are batch-installable with Ninite (https://ninite.com/).
Extras stuff that I specifically need but most won't below in spoiler.
Graphical:
• Davinci Resolve - Amazing video editor with tons of industry support.
• Adobe Creative Cloud
>Premiere Pro - Great quick video editor that really needs to get rid of its Windows QuickTime dependency
>Photoshop - Without a doubt the best raster image editor
>Illustrator - Great vector image editor for logos primarily.
>After Effects - I seldom use it but it's a good motion graphics compositor. Doubles as a great heater by making a project 4k.
• FFMPEG - Swiss army knife of audio and video encoding. This thing just about converts anything but is complicated to learn.
• OBS Studio - Successor to Open Broadcast Software. Great for screen recording or streaming.
Audio:
• PreSonus Studio One Professional 3 - Main audio workstation software
• Ableton Live Suite 9 - Secondary audio workstation software
• Native Instruments Traktor - DJing software
• LatencyMon - Great utility to see what's causing audio lag in production environments.
• dBpoweramp - A professional audio converter with tons of options.
Gaming:
• MSI Afterburner - Primarily used for changing speed curve on GPU fans.
• NVIDIA Inspector - Great to tweak specific games' graphical settings, such as FPS limiting for games like Skyrim.
Other additional stuff I use can be seen here (http://www.argonathrpg.eu/index.php?topic=116091.msg1825297#msg1825297).