I know the title may be confusing, but for me it would be my phone...more importantly Google Translate which just updated and now does Google Translate Tap. It shortens the translation process.
Here is a video of it in action
Not only has it improved by cutting the process, some of my cooks use the camera option which translates written word and the mic option.
And lastly, while it is not out yet...i am very very excited for this...It's a real time translation piece...You have to see it in action to fully grasp the awesomeness....Link Below
Link to their page (Waverly Labs)
So what is your favorite tool?