Venusaur

Venusaur used to be used more often in earlier RBY OU metagames, but it fell out of favor due to the amount of Psychic- and Ice-type moves, as well as paralysis, thrown around. Still, it stands out as a Swords Dance wallbreaker that isn't hindered by Rhydon, and it can cleave through bulky Water-types like Starmie, Cloyster, and Slowbro thanks to Razor Leaf: Razor Leaf is one of the most consistent ways to dispatch Slowbro in the tier, and deceptively few teams are actually prepared for it. Venusaur is one of faster viable sleepers in the tier, only being outsped by Jynx and Gengar. It can act as a soft check to Snorlax, which is unlikely to 3HKO Venusaur and may be forced into a Rest loop by Razor Leaf, letting Venusaur set up. Venusaur often can be a two-for-one with sleep as one "KO", and Swords Dance + Hyper Beam picking up the second.

However, a horrible defensive typing makes Venusaur harder to use effectively. It takes super effective damage from the very common Psychic and Blizzard, which will often deal heavy damage or force it out. Because of this, Venusaur adds very little defensive synergy to a team. Secondly, Venusaur's coverage is limited to Grass and Normal, allowing Gengar to hard wall it. Finally, it has competition with Victreebel. Victreebel also has STAB Razor Leaf, gets Wrap and Stun Spore, and has a higher Attack stat. It, however, has lower Defense and Speed than Venusaur. This means that, although Venusaur is less prone to being revenge killed by Tauros and never has to worry about Cloyster speed ties, it lacks the surprise factor and misses out on a few important damage ranges when compared to Victreebel, further narrowing its niche.