Ness (SSB)/Neutral attack/Hit 1
The main advantage the move has is that it comes out extremely quickly on frame 2. Because of this, Ness can cancel his jab (if it connects) into grab, known as a jab grab, a unique trait for Ness, Pikachu, Mario, and Fox. This gives Ness an extra option not present in many of the other lower tier characters (besides Luigi) and it is quite useful, as Ness's grab is one of the more powerful, at least when it comes to KOing (and it works regardless of if the opponent gets hit or shields the jab, although it does not work as well at long ranges or at higher percents). The move otherwise has very light knockback and is typical of most Smash 64 jabs (outside of DK/Yoshi) in terms of it's small range and quick speed.
It is not recommended to continue past jab 1 as at low percents, the second hit is not guaranteed (until around 20%-35% depending on the character) so the opponent can either shield it or even punish Ness if they have a frame 1 move. The third hit is not particularly powerful either, especially compared to Ness' throws. The first hit on itself is also unsafe on shield (at -8) and very unsafe on hit (at -7 at low percents), making it useless to use on its own.
Overall, Ness' jab is solid, largely due to its speed and jab grab potential. Outside of its jab grab potential however, it is a fairly standard and unspectacular jab.