Here's a list of some of the ones that I use the most. I'd bet that I have 50 or more that I use from time to time. I'm not sure what carrier that you have but if it is 4G Verizon you shouldn't be disappointed. I don't get 4G in my local area but it is available in most places that I travel.
Pandora - If you like music, this app is for you. Free to use and has a wide selection of music to choose from.
Beautiful Weather - Weather app - great for your home screen with good graphics.
Tapatalk - Fantastic app for mobile forum readers/posters. racing-forums.com is a supported forum. Huge battery saver of using a web based browser for reading forums and the like.
Are You Watching This - Don't miss a great televised sports moment. It alerts you to real-time updates of non miss moments in sports as it is happening.
TweetDeck - If you follow anything on Twitter this app is for you.
Wifi Analyzer - Locate open networks quickly so you can take advantage of the faster internet connection while on the road.
Words Free - Scrabble type game that you can play against anyone, anywhere.
Yahoo Messenger - If you use Yahoo for your IM.
Great Clips - If you're cheap like me and need a haircut quick.
I just looked and saw that the ATRIX 4G is running Android 2.3 When you get the update for Android 4.0 or higher make sure you check out something called NOVA Launcher. You'll love it. It'll open up many more features on your phone. In the meantime check out this website for more apps, free/paid alike.