Mario Kart Double Dash!! (2003)
Double Dash didn't win any awards at the time, but in retrospect it's one of my favorite Mario Kart titles, if only for the unique two racers-one kart mechanic.
Each character had a unique special power-up, and you could choose two racers per car. That meant you could tailor your character choices to your preferred play style and even keep an item in reserve, adding a few layers of strategy to the Mario Kart formula.