Name One App

I'm feeling a little sad these days.
For how great Android is, there are times like this in which I wish I had an iPhone just to try a few apps out.

I can manage to use an iPhone 4 at times and also have a "family" iPad at home, but since the 4 is not mine and I have a personal Nexus 7, I tend to leave the iPad to my mother who brings it with her every time she goes out - and I'm totally fine with it, since I couldn't stand with iOS or an iPhone as a daily driver for more than a few days.
But as I was saying, there are times like this in which I wish I had a side phone running iOS just to play a little with its awesome apps.
Yesterday was the turn of Storehouse. Then Paper for Facebook came out, and I started looking for iOS exclusive apps' bumping into the never-enough-mentioned Tweetbot, or the Fantastical calendar app. Oh, and Mailbox is awesome, too. The list could go on and on, you know it.

It's not that I need any of these apps, since Android does have a lot of great alternatives (and other beautiful and unique apps) - but as many people have stated over the years, the apps' stores (on any platform) are always flooded by tons of terrible apps, making it hard to find the golden ones in between.

So what I'm asking you here is exactly this. Share your opinion, and maybe make somebody happy, too.

If you were asked what is the exclusive Android app you couldn't live without, which one would you choose?
Tip: name a beautiful looking, slick app that not everybody knows, even though it's not exactly your favorite!

I will start off with Robird.
I use Twitter heavily on a daily basis, and though I like both Talon and Falcon Pro a lot this one is growing on me more than I thought lately. Also, v2.1 is soon to be pushed out in beta, and I can't wait to take advantage of the whole screen.

Now go!