Minecraft wiki entry for Best_enchantments_guide, associated text: Unbreaking III
Mending
Sharpness V (for general use) or Smite V (for fighting undead mobs, such as wither and wither skeleton farms) or Bane of Arthropods V (allows 1-hit killing of all arthropods; not recommended, unless for a spider farm)
Sweeping Edge III ‌[Java Edition only] (Deals more damage to multiple mobs while standing still, useful for XP farms, though you may accidentally hit your pets if they're too close)
Looting III (must-have for manual mob farms)
Fire Aspect II (Optional. Makes endermen a hassle to fight, since they teleport everywhere while on fire; hostile mobs that are set on fire set you on fire on melee attacks; cooks food dropped by cows, pigs, hoglins, sheep, chickens, rabbits, cod, and salmon) even in rain.
Knockback II (Optional. Can make drowneds and skeletons a hassle to fight; useful against creepers)