Well the maze wasn't a roadblock, so I guess you just want the final task?
My favorite (possibly because it's the closest the race has been to me) is the maze. It was intense seeing Chip & Kim struggle so much with it and Colin & Christie have a strategy and blaze through it. Another that I like is the field of clueboxes from Season 13, it's my favorite memory challenge.
The worst final challenge is "Eat a pizza". It wasn't even a large pizza. This is of course ignoring the seasons that didn't have anything: Seasons 1, 2, 7, 10. Though if include those last two as having a task, Season 10 is the worst because of how unfair it was to slow people.