This question is very interesting question and i have a Soni ericson Mobile his Model No J200 i this is just a simple phone nothing have so much features except from GPRS.
I have an Iphone , I love it because of all the apps and the ability to tweak it in a hundred different ways.
I have a Motorola Droid and absolutely love it. Aside from some small bugs here and there, it's a great phone. Works much smoother out of the box than the BB Storm I had before.
I have two phones. Both have lines and seperate lines. One is for business, the other for personal use.
Windows Phone 7 by Microsoft..well, in this coming October Currently touch HD running WM 6.5. If financially loose enough, get an iPhone OS4..of course, wait till it's released.
I have an LG Vantage, but I really want to get the LG vx9400 - its what Tony Stark used in the movie Iron Man
Currently i've chinese Mobile set Its very cheap and applicable for dual Sim system It's very nice one over here working