Battle Armor

 is a Pokémon ability introduced in the third generation. It protects from Critical Hits. Shell Armor is an ability introduced in the same generation with the same effect.

Description
Battle Armor and Shell Armor prevents the opponent from landing a critical hit

Pokémon with Battle Armor

 * Kabuto
 * Kabutops
 * Anorith
 * Armaldo
 * Skorupi
 * Drapion
 * Type: Null

As a Hidden Ability

 * Cubone (Normal)
 * Marowak (Normal)

Pokémon with Shell Armor

 * Shellder
 * Cloyster
 * Krabby
 * Kingler
 * Lapras
 * Omanyte
 * Omastar
 * Mega Slowbro
 * Corphish
 * Crawdaunt
 * Clamperl
 * Dwebble
 * Crustle
 * Escavalier
 * Shelmet
 * Turtonator

As a Hidden Ability

 * Torkoal
 * Turtwig
 * Grotle
 * Torterra
 * Oshawott
 * Dewott
 * Samurott

Trivia

 * Up until the fifth generation, Shell Armor was exclusive to Water-types.