The best controllers I ever had was the original xbox's Controller-S and the 360's too.
Right now Im using an imported DualShock 3 in white that I got off ebay 2 months before Sony released the black DS3 into the US. The L2 and R2 buttons could use some improvement especially when playing MotorStorm or Gran Turismo 5 Prologue.
If I remember Ben Heckendorn put the Sixaxis electronics into the 360 controller's body. Now that's what I would really love to get my hands on, but unfortunately Im not that good at electronics
Ben Heck's PS360: SIXAXIS-stuffed Xbox controller - Engadget