GameCube is the controller I'm most nostalgic for, but my GOAT controller has been, is, and will continue to be Xbox Elite Series 2.
The asymmetrical sticks. The comfortable triggers. The four perfectly-placed back paddles. It perfects the Series controller which improves the One controller which improves over the 360's. The battery is astounding and I like the customization they offer all around (stick tightness, LED color control, trigger stops, swappable parts). No gimmicks.
Nintendo's recent Pro offerings are comfortable but they don't edge out Xbox's. Sony's are too heavy, the batteries suck, and the added haptics/trigger behavior are things I don't miss when playing other platforms. I like 8bitdo and my Flydigi Vader 3 Pro is fine, but they lack a certain tightness on the sticks.