What is the one Android App that you would not want to uninstall from your device?

Really difficult question. At the moment I'd have to say my calendar. Not only do I know what's going on in daily life, but it's so well integrated with email and my phone. I can click on any names and send an email, or click on any number and initiate a call. Super useful.

And I know you asked for just one, but I can't resist adding a second. Outside of work I'd have to say the camera. I still get an "Oh, wow" kick when I take a picture or video and can immediately email it to someone.

It's not easy to pick up one app that is the best on Android platform.And I don't like the idea to put everything into only one app,for example,SUFBS.It's too heavy to run on a mobile device smoothly.

Instead I like the combination of apps on my HTC Hero,including ASTRO,AndFTP,ConnectBot,Twidroid.Another Android app that impress me is RemoteSMS.

Beyond the stock apps installed I'd have to say that Astrid would have to be the app that I'd have a hard time deleting. Even though the stock apps make Android useful from the start, I'd register a diminished experience if I had to forego a notes and todo app. You can get by using just the calendar, but then you're stuck with a ridged UI and methodology. Notes, todos, and calendar items are all very similar, but the right UI in context will make the gathering and sorting much easier. Apple even noticed this and have integrated both notes and todo into the mail.app on OS X. I use AK Notepad to collect notes and Astrid for todo items.

Astrid is a very competent todo list manager. It has all the bells and whistles, but leaves it up to you to figure out how much information you want to attach to an item. I like that. Two features that stand out are the ability to set a timer per item and syncing with Remember the Milk. You can also add items to the calendar as you create them in Astrid.

AK Notepad is the nicest of the notepad apps for Android. If you type a phone number, email address, or URL it will recognize what they are and create a link to the appropriate app for them. This comes in handy often. It also has the option to set an alarm for each note. To distinguish alerts coming from AK Notepad you can change the color of the alert LED. How cool is that?