New Mac User: App Reccomendations and Tips

I just got a new Macbook Air (2013 Haswell) and this is my first OS X device (I was looking for a Windows laptop, but this device offered more at the same price than any current Windows laptop).

I've spent the last two days tweaking everything to my liking and getting used to the OS but there's a lot to learn and there's a pretty massive app ecosystem out there to explore.

I was wondering if you guys had any apps you recommend a new Mac user should take a look at or any particularly useful tips/shortcuts/gestures I should know.