Sony's PlayStation 2 controller has been regarded by many as one of the best controllers ever made. It's ergonomic, responsive, and instantly familiar to most gamers. Unfortunately, Sony never produced a wireless version--but thankfully, Logitech does.
The Logitech Cordless Action Controller for PS2 ($40) has essentially the same layout as the PS2's standard controller but adds two buttons: one that changes the intensity of the rumble feature and another that allows you to establish a connection with your PS2 without pressing a button that may affect the onscreen action. Folks who are put off by the PS2's one design flaw--the segmented directional pad--will take to the Cordless Action Controller's directional pad, which offers a much greater range of control.
The RF-enabled wireless controller comes with a small receiver that plugs into any PS2 controller port. The receiver and the controller act independently from the system, which poses a bit of a problem. The controller turns on when a button is pressed or one of the sticks are moved. But to conserve battery power, it turns off after it's been idle for a few minutes. Warning: don't leave anything sitting on the controller or any of its buttons while the system is turned off or you run the risk of shaving many hours off of the controller's 50-hour battery life. As with the Xbox version, this controller runs on two AA batteries, and while it doesn't come with rechargeables, it does accept them.
The responsiveness between this controller and the PS2 is impeccable. Many PS2 games require extremely precise control, and the Cordless Action Controller worked every bit as well as a standard PS2 controller in this regard. Where a lesser wireless controller would have made acceleration difficult in Gran Turismo 4, pressing the button down slightly to head into a curve at a lower speed was just as easy as it is with Sony's controller. Likewise, Metal Gear Solid 3 requires analog movement of your character, Snake, and pressure-sensitive actions such as pointing your weapon without firing to hold an enemy hostage, was simple to pull off.. Really, the only area where the controller falls a little short is in the force feedback department--its rumble just can't match that of Sony's wired controller, so Snake's heartbeat when he hides from enemies just doesn't thump all that hard in your hands. But that's only a minor drawback.
Bottom line: if you're not a stickler for the rumble feature, the Logitech Cordless Action Controller for PS2 is by far the best option for PlayStation 2 gamers. The extra $15 is well worth the wireless freedom.