Jigglypuff (SSB4)/Dash attack
Description and usage
Jigglypuff leaps forward to tackle opponents with its head. The move is considered one of Jigglypuff's strongest ground moves for a few reasons. Firstly, It has good range, due to Jigglypuff leaping forward when using the move, which is something that Jigglypuff lacks in many of its moves. It is also fast for a dash attack, and can catch opponents by surprise with its speed. The clean hit has good killing power at higher percents, which combined with its fast startup makes it a very valuable tool for Jigglypuff, who often struggle to kill opponents due to its kill moves being difficult to land or highly situational. It also has good damage, both on the clean hitbox and the late hitbox, although the latter is to a lesser extent. Finally, the attack doesn't rebound, which makes it useful for neutralising many projectiles. 
However, the move also has some shortcomings which limit its usefulness. Like with most dash attacks, it has a lot of ending lag, so if the opponent shields the move, Jigglypuff is left open for a punish. Additionally, unlike most dash attacks, it has very little base knockback, making it unsafe at low percents. The late hit lacks kill power, limiting the move's range when attempting to kill with it, and its usefulness is also somewhat hindered by Jigglypuff's poor running speed, making it unsuitable for punishing in some circumstances.
Overall however, it is considered one of Jigglypuff's best options on the ground for killing, dealing damage or punishing due to its speed and power, and its ability to neutralise projectiles is incredibly useful since Jigglypuff generally struggles against projectiles due to its general lack of range and mobility..