Hypno

Hypno has the best typing in RBY, serviceable base stats, and the uncommon ability to spread both sleep and paralysis through Hypnosis and Thunder Wave. While these qualities are good in a vacuum, Hypno is unfortunately outclassed by the most dominant Psychic-types in the tier; Starmie and Alakazam have Recover, while Exeggutor has Explosion, giving all three great options to play out of potentially difficult situations. Hypno, meanwhile, is stuck with Rest as its only recovery option and no way to match or break through its Psychic-type cousins in most scenarios. This means that Hypno struggles both defensively and offensively in practice, failing to find real defensive niches and to threaten much more than Thunder Wave on its Psychic-type foes.

Hypno's niche mostly exists alongside these superior Psychic-types, rather than in their place, offering unusual options its competitors lack or struggle to combine. For example, one may use their Exeggutor to lure a paralyzed target into blocking its Sleep Powder, KO it with Explosion, and then follow up with Hypno's Hypnosis for easy sleep. However, there are two use cases for Hypno as a primary Psychic-type that are worth mentioning. Hypno is better than either Jynx or Exeggutor at sleeping a foe, spreading paralysis, and later absorbing sleep thanks to its decent Defense, which allows it to run Rest without being overwhelmingly punished, thus potentially healing its own paralysis so that it may absorb sleep at a later point. Jynx struggles with using Rest due to its terrible Defense, while Exeggutor struggles because of Ice-type moves breaking its Rest cycles. Hypno's diverse toolkit also includes oddball moves such as Submission, which allows for more pressure on Chansey than the other Psychic-types can usually offer, and it can lead to some extremely favorable scenarios with some lucky paralysis and critical hits. These advantages are incredibly specific and marginal, though, so Hypno is nothing more than a fringe pick in RBY OU.