Data: email, texting, miscellaneous apps, music. document management, surfing the web. And of course an occasional phone call or two every now and then. I am on the lowest voice plan available.
Sent from my Verizon Black 64GB iPad 2 w IOS 5.0.1 Update using iPF.net
Glad you asked because the most specific thing I use my iPhone for the most & on a daily basis throughout the day is Weight Watchers. I do not attend meetings, I do not use the computer. I strictly use the WW mobile app to do everything. I use it more than any other feature or app on the iPhone. It is something I didn't even think about until you asked.
Texting first and foremost. I am a big texter and rarely "TALK ON THE PHONE"...I use Safari a lot and since having the iPhone, my laptop usage has dropped by about 75% as I do everyting on my iPhone. Emailing, game apps, weather, college football scores, Facebook...