In the earlier Pokemon games, players had to use an HM to perform certain tasks that also doubled as moves.
The best HM slave : r/pokemon
Pokemon Red (I patched the game to give myself a random starter as well as to allow my hm slave to learn every hm) : r/PokemonHallOfFame
Top 10 HM Slaves in Pokémon - LevelSkip
Top 10 Mega Evolutions For The Diamond And Pearl Remakes
Top 10 HM Slaves in Pokémon - LevelSkip
HM Slave [PART 2] by sparklingdemon on DeviantArt
Top 10 HM Slaves in Pokémon - LevelSkip
Best HM Slave Pokemon Heartgold - Pokewolf
Best Unova HM Slaves For Your Gen V Pokémon Team – FandomSpot