For me it was iTranslate Voice.
I was stunned at how good it works

Basically, you choose input and output language (and there are tons of languages)

You press the button and start talking on your language (provided you selected it as an input).

App translate it to (any selected) output language and it even SAYS it out loud.

Great when you are in a foreign country and trying to find something.
I tested it with few languages and they all work great.
I tested it in Japanese with business partner of my company and we communicated perfectly
Friend of mine sent me a SMS from Chile and he said that app saved him time 1000 times

It works better on iOS but it also works on Android.

(And it even recognize swearing)

And its cheaper on Android

Try it. Really great stuff.
I bought it for 8$ (iOS) just to show the makers respect. Very very good work