In the world of open-source software you can find a free alternative to almost any software. But sometimes software is worth paying for.
Sublime Text 2 - This text editor is amazing, I've been using it for a few years. I've tried Atom and use it on my Windows desktop but where Sublime shines in on my MacBook Pro, truly beautiful piece of software.
Photoshop CS5 - CS5 and CS6 are both great software, try and avoid anything newer than CS6 as Adobe has moved to Photoshop CC (Creative Cloud), a subscription based software.
Visual Studio - One of my favorite IDEs, it's hard to find a competitor for Windows based development, it also supports a ton of other languages besides C# with the help of addons.
Spotify Premium - I listen to a lot of music and Spotify if great, if you half qualms with "you don't own the music!" then you might want to avoid Spotify but for those of us who want easy access to music with mobile streaming Spotify is it.
Steam - While technically free Steam is a gateway drug, if you like PC gaming (don't be a peasant!) then you need Steam.