An original DualShock 2 that came with my PS2 Slim. No other controller beats it imo, it's well built and weighty with great feel. I hooked it up to my PC with a simple PlayStation>USB adapter lead, and it plugged straight in with no drivers or anything
I had used a joystick previously, a Logitech Freedom 2.4, but the buttons I used for rear steer (the only ones suitable) tended to crap out on me. This bit me in the Anaheim King of the Hill, where, in a race with Max, the rear steer failed and I slammed into the wall upside down