Squashing annoying lapped cars and getting rid of even more annoying parachutes.
Actually, if no one is around, it either means a big gap in skill/handicap/kart type, or it's pure luck and usually very rare. Basket ball is another type of annoying powerup, and they are pretty frequent, so in case you have only swatters and too much basket balls flying into you, you could use swatters to hit others once a sufficient number of basket balls hit you