I made a discovery playing PokéRogue today, which truly surprised me and searching this thread it seems it hasn't been mentioned before.
Bouffalant, the Pokémon with the ability Reckless and the signature move which is a Double-Edge clone except it takes slightly less recoil, learns 2 recoil moves: the aforementioned Head Charge, and Wild Charge, and it's only ever learned these two recoil moves.
The way I discovered it was PokéRogue gave me a Take Down TM and I thought I'd teach it to Bouffalant in the early game because it's better than Tackle, and it was incompatible. I can understand it to an extent if they wanted Bouffalant's whole thing to be "it's reckless and uses recoil moves but only the ones that deal less than 1/4 recoil because afro padding!!" but Wild Charge deals 1/4 recoil itself anyway.
The link between recoil moves and abilities that interact with them has always been dodgy, especially with Rock Head where a lot of Rock Head mons only learned Double-Edge for a long time, but due to Head Charge existing it feels way more pronounced here. There are deceptively few real recoil moves anyway, the main ones missing here are Take Down and Double-Edge. Maybe they didn't want Double-Edge because it's the same BP as Head Charge but I don't think Bouffalant was breaking the game with 130BP Head Charge anyway.
Flare Blitz has only been learned by Fire-Type Pokémon, Solrock, Koraidon, and Terapagos(?), and besides Terapagos they all have genuine Fire-Type affiliation. Head Smash probably doesn't make sense to exist alongside Head Charge despite it being learned by more mons in general. Funnily enough Wave Crash could fit here, Bouffalant is one of those "randomly learns Surf" mons and that was less common by Gen 5 with the only other example being Audino. Bouffalant isn't in Gen 9 and Wave Crash is currently only learned by Water-Type Pokémon, but that could be a cool addition for the future.
Bouffalant, the Pokémon with the ability Reckless and the signature move which is a Double-Edge clone except it takes slightly less recoil, learns 2 recoil moves: the aforementioned Head Charge, and Wild Charge, and it's only ever learned these two recoil moves.
The way I discovered it was PokéRogue gave me a Take Down TM and I thought I'd teach it to Bouffalant in the early game because it's better than Tackle, and it was incompatible. I can understand it to an extent if they wanted Bouffalant's whole thing to be "it's reckless and uses recoil moves but only the ones that deal less than 1/4 recoil because afro padding!!" but Wild Charge deals 1/4 recoil itself anyway.
The link between recoil moves and abilities that interact with them has always been dodgy, especially with Rock Head where a lot of Rock Head mons only learned Double-Edge for a long time, but due to Head Charge existing it feels way more pronounced here. There are deceptively few real recoil moves anyway, the main ones missing here are Take Down and Double-Edge. Maybe they didn't want Double-Edge because it's the same BP as Head Charge but I don't think Bouffalant was breaking the game with 130BP Head Charge anyway.
Flare Blitz has only been learned by Fire-Type Pokémon, Solrock, Koraidon, and Terapagos(?), and besides Terapagos they all have genuine Fire-Type affiliation. Head Smash probably doesn't make sense to exist alongside Head Charge despite it being learned by more mons in general. Funnily enough Wave Crash could fit here, Bouffalant is one of those "randomly learns Surf" mons and that was less common by Gen 5 with the only other example being Audino. Bouffalant isn't in Gen 9 and Wave Crash is currently only learned by Water-Type Pokémon, but that could be a cool addition for the future.
Vespiquen is the easiest to explain: it orders its swarm to attack the target with their poisonous stingers. Combee is not noted to have a poisonous stinger in any dex entry, but it's extremely plausible given the well-known attributes of real bees. The question is: why doesn't Combee learn Poison Sting? If Vespiquen's Poison Sting is performed by baby Combee, surely Combee can perform the move itself? Does each Combee carry such a miniscule amount of poison that an entire swarm is required for any real attack, even a 35 BP one?
Cacnea's delivery method is obvious: the spines covering its body. The poison part is less clear. Cacti spines are not poisonous, and nothing about the Cacnea line screams poison. It's possible Game Freak decided "plant = poison" was good enough.
Sandshrew is the most mystifying to me. First, neither it nor its evolution are depicted as using poison. If it had poison, it would probably apply it with its claws, but claws are seemingly not treated as a proper means of using Poison Sting. After all, Hisuian Sneasel's claws drip with venom, but it doesn't learn the move. Is it supposed to be for Sandslash's spines (which, again, are not poisonous) and then they just gave it to Sandshrew too?
Budew learns the move as well in Legends: Arceus, though, despite lacking both. Budew is no doubt poisonous, but I fail to see how it stings. Budew actually has Roselia's entire learnset in Legends: Arceus. Gameplay purposes, no doubt.
Naganadel, the Poison-type "UB Stinger", does not learn Poison Sting.
Kirlia, 
Mienshao, 
Meowscarada, and others can easily be seen executing a spinning kick. Among Ice-types, the distribution is quite a bit more lax.
