Some stuff you should install

ShareX

Upload things, lots of things, screenshots, files, clipboard contents, video screen caps. I think you get the idea, an open source more flexible version of things like lightshot and gyazo.

Atom

A very nice looking text editor, supports plugins so you can extend the functionality if needed. It's more useful for programmers because of a lot of it's highlighting features. Either way though it's free and is way nicer than notepad.

ConEmu

Do you use the command line on windows? Do you hate it with a passion? So do I so go get ConEmu, it runs all your command line applications in a command line that isn't horrible. It's awesome for multitasking due to the tabs and it has some great features like flat out overwriting the normal command line to run ConEmu instead. Oh, and it's opensource.

Deluge (Please stop using μTorrent)

It's pretty, it's lightweight, it's bullshit free, it acts like μTorrent and it's opensource meaning that you most likely will not see any adware in the future either which is nice. Oh, and it's multiplatform so mac users can use it to.

f.lux

Changes the hue of your screen according to the time of day, if you're doing some colour sensitive work don't worry you can disable it for a bit.

GOG Galaxy

Like steam but DRM free. Still in early development but I've run into literally no issues, games are cheap too so that's nice.

IObit Uninstaller

Really nice for batch uninstalls, be careful when installing though as it does try and install some excess.