My phone is a Sony Ericsson Xperia Active and an Asus Transformer TF101 (with cyanogenmod 10.0). I am located in Finland so these apps may or may not exist in your market.
Updated 201308. Easy to go to play.google.com and see which you've ever installed :)
flashlight - There's a ton of these out, useful anyway. Mybookdroid - Scan barcode of your books and adds them to your library. Synchs with goodreads.com . Google Translate - Nicer than using the web page. Collins Swedish-Finnish words - Paid version includes pronunciation as well. After trial expires only random word widget works - which is what I use it for. Andropas - Public Transport around Helsinki Metropolitan area - quite awesome. Native browser / Opera Mini - I used the Opera Mini for a while because it was quite fast. But after an update it sometimes did some not so nice refreshes of the page - for example after writing a post in a comment in facebook - which caused all the text to be gone. The native also works with google docs which is a big plus. These days google chrome is also a good alternative. Google Maps - Good enough free GPS-alternative. RealCalc Scientific - most of the tools are a mile or three over my head - but I've used it occasionally :) Irssi ConnectBot - Some extra features compared to the normal ConnectBot that makes irssi via ssh/screen a lot smoother. Irssi Notifier - Get notifications when for example you've been hilighted on IRC AndroIRC - Useful when I'm too lazy to jump through the ssh hoops :)
Zeam Launcher - makes the interface more customizable, "thinner" - not so much extra stuff - what I like most is that you don't have to do as much flipping between screens when looking for an app. Skype - works so/so, but it does the trick :) Advanced Task Killer - Kills apps to free up resources. This page is also very slim -> I like. Elixir 2 - See which processes are using your system Fing - Wake On LAN start my desktop :) WiEye - Check out which channel you should put your wifi on :) Ftp Server - Easy way to transfer files to the Transformer Hipmunk - Find cheap flights based on agony is fun :) KeePassDroid - Sync password database - can be integrated with Dropbox. PerfectViewer - Read comics Spotify - Music! Sveriges Radio - Listen to Swedish radio. Apparently listening to non-live shows is a bit buggy. Yelp - Find someplace to eat