Harden
Type: Normal
This makes your defense rise. Using it enough will make you pretty much invincible, but by then you'll probably have fainted. Metapods and Kakunas that only have Harden are very dumb - they can't win*.
*Actually a Lv.100 Metapod with only Harden could beat a lv.15 Magikarp with Splash and Tackle. Metapod would run out of PP for Harden, use Struggle, and win!
Harden is learned by:
Metapod (first move)
Kakuna (first move)
Graveler (Lv.27)
Grimer (Lv.5)
Onix (Lv.23)
Krabby (Lv.16)
Staryu (first move)
Pinsir (Lv.25)
Kabuto (first move)
Guraiga (Lv.14)
Harisen (Lv.10)
Maggumaggu (Lv.22)
Saniigo (Lv.7)