Vault Boy

Vault Boy is seen smiling, with one eye closed, an arm outstretched, fist clenched with a thumb raised
Vault Boy checking the blast radius, not giving a "thumbs up"! Ouch

Vault Boy History

The Vault Boy character is Vault-Tec's mascot and is a recurring element in Vault-Tec products in the game world. This includes the Pip-Boy, where the Vault Boy illustrates all of the character statistics and selectable attributes. From Bethesda's Fallout 3 release onward Vault Boy models all of the clothing and weaponry as well.

The character was originally designed by Leonard Boyarsky, based partly on Rich Uncle Pennybags' aesthetic from the Monopoly board game, and drawn for Fallout by George Almond for the first few cards and by Tramell Ray Isaac, who finalized the look of the character.

Reference: Wikipedia entry