From Bulbapedia, the community-driven Pokémon encyclopedia.
Moves. There are a lot of different moves, and the majority of Pokémon can learn a wide array of moves. But some make you wonder: why can't they learn that move? Here's the moves that (in my opinion) are missing from certain Pokémon's movepools. I will sort them by move and also give reasons for my choices.
List of moves
The moves will be sorted in alphabetical order.
Pokémon that should know Acid Spray in my opinion:
Bellsprout, Weepinbell, Victreebel, Scrafty: Pokédex entries mention that these Pokémon are capable of spitting acid.
Spinarak, Ariados, Joltik, Galvantula: Spiders tend to use all kinds of acids to melt their prey's insides with.
Carnivine: Flytraps like Carnivine also generally use acids to help digest their prey.
Pokémon that should know Agility in my opinion:
Sandile, Krokorok, Krookodile: Crocodiles are capable of moving extremely fast for short periods of time, and Feraligatr can learn Agility, so...
Pawniard, Bisharp: After seeing Pawniard in action in BW041, it definately seems capable of rapid movement to me.
Pokémon that should know Air Slash in my opinion:
Shiftry, Drifblim: Both are related to winds and have sharp-looking appendages with which blades of air can be formed.
Gabite, Garchomp: Garchomp's Pokédex entry states that it can fell trees with blades of air when it runs. Gabite's physical shape resembles Garchomp, so it would be able to do the same.
Axew, Fraxure, Haxorus Their tusks look capable enough to create blades of air with. If Oshawott and Sewaddle can do it...
Gallade, Pawniard, Bisharp: They can create blades of air with their arm blades.
Pokémon that should know Aqua Jet in my opinion:
Horsea, Seadra, Kingdra: These Pokémon are very fast, and I think Aqua Jet suits them.
Goldeen, Seaking: These fish Pokémon can swim very fast, so they would be able to lunge at high speeds.
Huntail, Gorebyss: These fish Pokémon aren't very fast swimmers, but they can lunge very fast to catch prey.
Pokémon that should know Aura Sphere in my opinion:
Clefairy, Clefable, Chansey, Blissey: They all have this mystical and cutesy aura around them, which makes them candidates for Aura Sphere, IMO.
Ralts, Kirlia, Gardevoir, Gallade, Gothita, Gothorita, Gothitelle: These Pokémon read emotions of other people, which means they're proficient with aura.
Meditite, Medicham, Darmanitan: Through hardened meditation, their aura becomes so strong they can harness it in battle.
Celebi, Sigilyph: This elusive move will add to their mystery factor.
Pokémon that should know Autotomize in my opinion: