Luigi (SSB4)/Down aerial
Luigi performs a downward corkscrew kick. It is a meteor smash on aerial opponents, though its power is lacking. Unlike past games, the sweetspot is timing-based instead of position-based, making it comparatively much easier to use.
This move has many uses. The combination of wide autocancel windows and Luigi's floatiness make it very useful in air-to-ground combat, as it carries little risk if the opponent isn't right next to Luigi. Due to the late hit having the Sakurai angle, it can occasionally trip opponents, further improving its utility in approaching. Combined with all the aforementioned properties, it is a formidable edgeguarding tool. Even if it doesn't meteor smash, it can still be useful for gimping recoveries, since Luigi will almost always be able to make it back to the stage. Finally, it can be used as a follow-up after a down throw, with the clean hit also being a good combo starter. Overall, like every other aerial attack Luigi has, it is an all-around useful move.
Luigi's down aerial was buffed in patch 1.1.1, as it increased the hitbox size of its clean hit, making it easier to land the meteor smash.