What are some of the linux must have apps?

Hey I am also using Linux and as now I am on holiday so whole day I keep on using it and now I have noticed some of the applications I use more often than others. You download a numbers of apps in your Linux , The applications vary from music players, browser, photo management, disc burning tools and email clients etc etc. The list just goes on and on, so I cannot list all but I am listing some of my favorite for you.

1. Unison is one of the best backup programs that are so much popular for the new Linux users. With the help of this you will be capable of backing up files and folders to local and remote locations.

2. Mondo is a text-driven system backup & restores utility. It is reliable and works well with a range of file systems.

3. Opera is among the solid browser and as you know that it works so well and you can open lots of windows as the same time using app.

4. Guake is a semi-transparent drop-down console and this software is always ready at the tip of your fingers.

5. Virtual Box is a must for you if you want to run another/multiple operating systems within an operating system (OS).