All the apps listed below are compatible with Yosemite, the current version of Mac OS.

(1) Knock – You can unlock your Mac by simply tapping your iPhone screen or your Apple Watch without having to type any passwords.

(2) ImageOptim – Always run your images through ImageOptim before upload them on to your website. The Mac app will crush the size of your image files without affecting the visual quality.

(3) Air Browser – This will put your favorite websites in the menu bar so you can access them from any screen with a single click. The sites can be configured to auto-refresh on open.

(4) Duet Display – Use your iPad or iPhone as an extra display for your Mac. Connect the iOS device to the Mac with the USB cable and use the touch-screen to interact with your Mac apps.

(5) Infinit.io – Easily send files and folders of any size from your Mac to another device be it a Windows PC, iPhone, iPad, Android phone or a Mac itself.
    

(6) Spectacle – This is a useful windows management app for Mac that lets you move and resize windows with configurable keyboard shortcuts. You can also move windows between multiple displays too.
  

(7) Toggl – Time tracking software for your Mac that sits in the status bar for quick access. Add "#hash-tags" to tasks and your tracked hours are also synched with the web.

(8) Authy – Not exactly a Mac app but a Google Chrome extension that you cannot do without. It lets you log into online accounts that require 2-factor authentication without requiring the phone. 

(9) MacDropAny – You can easily sync any Mac folder with Dropbox or Google Drive without having to move them to a common folder.

(10) Fluid – This will turn your favourite website into a real desktop app for Mac that will reside in the Applications folder and you can launch from Spotlight search.