Nano 2nd Generation
The second version of the Nano from Apple had most of the flaws that were let go in the first version corrected. In fact I use a Silver 4GB Nano 2nd Gen for running each day and going to the gym.
I use it with a Speck arm band and the Speck brassard for my Nike + iPod running kit's transmitter. You may not know about this set but with a Nano, it allows a runner fairly exacting information about time and distance while on a run. The velcro fastened transmitter lets me move the transmitter from my New Balance training shoes to my Newton Running competition shoes easily.
The Nano 2nd Gen is perfect for any audio file playback... and frankly that about all a Nano should really be used for even though Apple has added radios and cameras to them recently.
The 2nd gen color LCD screen is easy to look at, the device itself is small. One of the problems with the 2nd Gen is the outer housing is basically an extruded aluminum tube that's been flattened.
All of the device... logic board, headphone jack, battery and LCD slide into the hollow tube from the bottom. And that is now the biggest problem. As of 2011 this model has been out for nearly 4 years, and the batteries in most of them are giving out. As a Lithium Polymer battery ages it's chemistry un-binds and the battery expands in size. The battery package actually expands and wedges all of the parts inside the tube making repair or replacement of anything in it impossible because you will damage things while trying to get it out.
Additionally, besides not being able to easily slide the aged battery out, replacing the battery in this model is impractical. The cost associated with de-soldering and soldering in a new one make it impractical relative to replacement.
If you have a working Nano 2nd gen, treat it nicely and will work for years provided you read my article on how to charge the battery. Over charging the battery will reduce it's potential 7 year life to about 18 months.
The article is here:
If someone tries to sell you this model used, decline. It is past it's moment and will bring hardside to you.