Fallout: New Vegas Creatures

Arthropods
All of these creatures are affected by the Entomologist and Bug Stomper perks.
 * Cazador
 * Young cazador
 * Legendary cazador
 * Bloatfly
 * Giant ant
 * Fire ant
 * Giant ant queen
 * Mantis
 * Giant mantis nymph
 * Giant mantis female
 * Radscorpions
 * Small Radscorpion
 * Bark scorpion
 * Bark scorpion Hunter
 * Giant radscorpion
 * Radscorpion Queen
 * Radroach

Humanoid

 * Ghouls (Mutated creature, not affected by Purifier or Abominable however)
 * Feral ghouls (Abomination, affected by Purifier and Abominable)
 * Glowing One
 * Feral ghoul reaver
 * Feral ghoul roamer
 * Feral trooper ghoul
 * Glowing trooper ghoul
 * Overseer
 * Vault security officer
 * Humans
 * Super mutants (Super Mutant/Abomination, affected by Purifier, Abominable and Mutant Massacrer)
 * Nightkin
 * Ghost People (Dead Money DLC)

Non-humanoid

 * Bighorner (Animal)
 * Bighorner calf
 * Bighorner bull
 * Brahmin (Animal)
 * Malnourished Brahmin calf
 * Centaur (Abomination, affected by Purifier and Abominable)
 * Evolved centaur
 * Giant evolved centaur
 * Coyote (Animal)
 * Coyote Alpha Male
 * Coyote Den Mother
 * Coyote Pup
 * Dog (Animal)
 * Legion mongrel
 * Fiend guard dog
 * NCR guard dog
 * Nightstalkers (Abomination, affected by Purifier, Animal Friend (though not technically an animal) and Abominable)
 * Legendary night stalker
 * Young Night Stalker
 * Giant rat (Animal)
 * Rodent of unusual size
 * Mole rat (Animal)

Plant creatures
All mutated plants are affected by Purifier and Abominable.
 * Spore plant
 * Spore carrier
 * Spore carrier savage
 * Spore carrier brute
 * Spore carrier fledgling

Reptiles

 * Deathclaw (Mutated creature/Abomination, affected by Purifier and Abominable)
 * Deathclaw baby
 * Young Deathclaw
 * Deathclaw alpha male
 * Deathclaw mother
 * Legendary deathclaw
 * Blind Deathclaw
 * Gecko (Considered animal for Animal Friend, Hunter and Animal Control)
 * Little gecko
 * Golden gecko
 * Fire gecko (Doesn't count toward Animal Friend)
 * Legendary Fire Gecko
 * Lakelurk (Animal for purposes of completing Animal Control, but not Animal Friend)
 * Lakelurk king

Fish

 * Fish

Avians

 * Raven
 * Bird

Extraterrestrials

 * Alien
 * Alien Captain

Legendary creatures
For a list of legendary creatures, see Fallout: New Vegas legendary creatures. This page goes into more detail about each legendary creature.