I hate one version of the Sega Saturn pads, the flatter-non-genesis-like one, the l/r-buttons are just a tad to easy to press so I regularly tap them accidentaly.
Also I HATE the D-Pad on the MadCatz Dreamcast-controllers. What is the purpose of having 6 standard buttons for fighting games when the D-Pad doesn´t allow precise movements in a straight line? It´s almost as awful as the first Logitech Wingman gamepads, the ones which now have blue buttons, they originally came with red ones, a standard joy-connector instead of USB and I swear that they inserted the contacts 45degrees rotated, I never could walk in a straight line in OMF with these.
I like the standard XBox-controller though, I´m waiting for a driver to use it on a pc, it is a standard USB-controller after all.