2010: 343’s hidden climber was really cool, unfortunately it was just inches too slow to make Einstein. There was a plastic shroud around the whole robot and the top had a pair of flaps that covered all but the topmost piece of metal so the whole thing disappeared for most of the match allowing them to slide through the tunnels, but was released at the end for an unexpected (the first time) climb.
2013: 254, the 7 second full climb was mind-blowing!
2015: 125’s can grabbers, stupid fast tennis balls on fishing rods. I was in shock when we played with them how fast and consistent they were.
2017: I’m surprised someone hasn’t mentioned the shooters of 971 or 125, specifically their feeder mechanisms