howandwhy99
Adventurer
1st level is something of a spectrum of <1HD to 2+HD solos so to speak. Paging through the MM 1e I can find a few that aren't overpowered by special abilities. Popularity is probably the best mark of being iconic though.
Baboon
Badger
Centipede, Giant
Dog, Wild
Dryad
Dwarf
Elf
Frog, Giant
Gnome
Goblin
Green Slime
Halfling
Herd Animal
Hobgoblin
Horse
Jackal
Kobold
Men
Mermen
Mold
Orc
Piercer
Skeleton
Spider, Large
Stirge
Zombie
Baboon
Badger
Centipede, Giant
Dog, Wild
Dryad
Dwarf
Elf
Frog, Giant
Gnome
Goblin
Green Slime
Halfling
Herd Animal
Hobgoblin
Horse
Jackal
Kobold
Men
Mermen
Mold
Orc
Piercer
Skeleton
Spider, Large
Stirge
Zombie