I saw your post and everyone else's and decided to make an organised mega-list from the thread. I think I'm a bit late and nobody will see it (posted it as it's own comment), so I'm posting it as a reply here to get it a bit more visibility.
Clover: allows tabs in your file explorer. (like the tabs in Chrome, but in file explorer instead)
7zip: Basically WinZip, but better in almost every regard. And it's still free!
Everything: Instant computer searching. Much better than the default Windows search.
UBlock Origin: Available in your browser's extension store. Free, of course. It's pretty much AdBlock, but does a whole lot more. Make sure you get Origin, though.
RES: Reddit Enhancement Suite. If you're using Reddit without this, you're really missing out. It adds a shitton of features and it'll ruin vanilla Reddit for you.
Bitdefender: Helps you to not get viruses.
Malwarebytes: Helps you to get rid of the viruses that BD missed. There is a paid version, but the free ver is pretty good.
Musicbee: Like iTunes, but you know, better. Because it's not iTunes.
VLC: Free media player, works pretty well. Some people like it, others don't.
Media Player Classic - Home Cinema: For those who don't like VLC. I run it with the K-lite codec pack and it is amazing.
Steam: Largest online video game retailer. Desktop app allows you to organise your library of games and play them at any time. But you already knew that.
Origin: Like Steam, but for Satan EA.
GOG Galaxy: Again, similar to Steam. Short for "Good Old Games - Galaxy", GOG-G is a store that is almost entirely dedicated to the old games. HoM&M III (the original), they got it. Neverwinter Nights, they got it. Master of Orion I and II, they got it. It's nostalgia and cheap prices all rolled into one.
Teamspeak 3: Voice Over IP program that allows you to set up a server (most people pay a company to host for them) for people to connect to and chat on. Used by online gamers around the world.
Discord: Similar to TS3, but has a browser and phone app and is entirely free to use.
Gimp: Free photoshop (Not as powerful as photoshop, but still very useful)
Paint.NET: More powerful version of MSPaint
Lastpass: Stores and designs passwords. Has a Subscription based premium mode
1Password: Similar to Lastpass, does require a $65US initial payment though
KeePass: Similar to the above two, but free!
Auto-hotkey: Scripting engine for your computer. Sorta. You can make scripts that run on certain keys (eg, setting up media controls (play/pause/FF/RWD/etc) to certain keys/key combinations). Free, and fairly powerful.
Rainmeter: Pretty cool desktop tool that lets you set up widgets (like the ones from vista/win7) to do all sorts of shit. Bit hard to get into (I tried it a few years ago and it was a bit complicated), but it's a definite 10/10 app. Check out /r/rainmeter for tips n shit.
F.Lux: Changes the brightness (well, more of the "blue-ness") of your screen depending on the time of day. Very useful!
Ninite: Website that allows you to add/update most of these programs to a fresh PC. Obviously not a program, but veyr useful given this thread's content.
Notepad++: This probably belongs in the technical section but w/e. It's pretty much the Notepad windows program, but it allows you to save your documents in almost any text-based format. I use it all the time at uni for coding in C/C++, and it also changes the appareance of the words in the code depending on the language.(Words like if/else/while/do show up in blue when coding with C/C++)
Telegram Messenger: A messaging app that's basically WhatsApp, but has a desktop client, web client and even a windows phone client. Has so much more features (replying to specific messages, "secret" chats, etc.) and even had older features (end-to-end encryption) before WhatsApp.