ASCii Stick FT (Dreamcast) is hands down the best controller I've used. The optical joystick is the smoothest and most responsive control I know of. The buttons aren't the best but have never given me a problem. The built in rumble takes playing REZ, or Ikaruga, or Zero Gunner II to the next level!
Frustratingly, ASCii changed the length of the stick on their 3 models of optical joysticks for Playstation, and apparently the ASCii Playstation optical sticks aren't Dualshock compatible (or something) so they don't function on PS2.
I have the PS2 version of that controller and the clicky thumbstick seems to require a bit extra pressure to be sure I'm getting the input I desire from the d-nub. It's a neat novelty, but not a favorite of mine.

