The Dual Shock 2 is the official Sony brand controller for the Playstation 2 console. It was originally offered and is usually seen in black, but is now offered in a variety of colors.
The Dual Shock 2 is, in my opinion, one of the more comfortable controllers on the market. It fits very well in the hands, and has a nice weight to it. It is essentially the same as the Dual Shock for the PS1, but now has analog buttons, which register the amount of pressure being applied to them. However, most of the buttons don't "feel" analog, and the feature is not used very often.
This controller is a wired controller, with a cord length of about seven or eight feet. If you don't care about wireless, this is the controller to get for the PS2.