* BaseBreaker: Some say he is a good character, but it seems everyone either loves or hates Koopa.
* DemonicSpiders: Heaven help you if Mario or Luigi decide they want to be in first place. With their infinite stars, you will never stop them.
* GameBreaker: The Feather often allows racers to jump over walls for huge shortcuts in a game where traditional shortcuts are rare and minimal. Because of this, [[http://www.youtube.com/watch?v=Ojbpe2ZXxss the TAS]] abuses it to no end.
** The heavy characters (Bowser and Donkey Kong jr.), despite their low acceleration, have the highest top speeds in the game. For expert players, Bowser and DK are easily the best choices for tearing through courses at top speed-- provided they don't hit anything. The inverse is true for the lighter characters-- they have better acceleration, but their top speeds aren't as high as the heavyweights.
* GoddamnedBats: plenty of obstacles, but particularly the Monty Moles that malevolently jump out of their holes just in time to hit your kart, stop your momentum entirely, and slow you down until you press R enough.
* NauseaFuel: Motion sickness from all the driving, moving backgrounds, crazy colors of Rainbow Road.
* ThatOneLevel
** Rainbow Road due to the total lack of guardrails between you and the BottomlessPit, exceedingly narrow track, and special Thwomps that can wipe you out at the mere touch.
** Donut Plains 3 also fits this trope because of the double hairpin and the narrow--and broken--bridges.