The Nokia 3210 is the most popular phone on the market, especially with teenagers- and you can see why. It looks great, and is packed full of features. The 3210 offers interchangable covers, which are available from almost anywhere and cost from £5 up to about £20.
Also, the battery life is excellent with it remaining on stand by for up to a week, and a talktime of a good five hours.
It has an internal aerial, making it more compact and also some excellent menus. The 3210 has a choice of three games, with an optional extra two if a data cable is purchased. It has a large phone book memory, and also predictive text input making sending text messages a breeze. The 3210 also has a great selection of ringtones, with the ability to create your own and send one to your phone from the internet. I reccomend yourmobile.com or boltblue.com or mobilemelodies.com
It has a clock, alarm and calender, along with a very easy to use and useful calculator. It charges up very quickly, and is reasonably lightweight and small.
Off hand I cannot think of any disadvantages, and would reccommend this product to a teenager who wants a lot of features in his or her mobile.