Toy Model

Knick Knacks are toys that can be picked up in Fallout 4, but cannot be salvaged or broken down. These are mostly used in decorating but can be sold for a fair amount of caps.

The standard versions of the robot models (not the parts models), can occasionally be found at random in the Vault-Tec lunchboxes scattered throughout the game. Clicking on the lunchboxes yields a random small item, either a consumable or a small junk item. With each one, there is a chance to receive one of the robot models.

Although the models can be sold, the parts cannot. Attempting to sell any of the parts models to a vendor will result in the message, "You cannot sell quest items." This would seem to suggest that they may be used in a quest somewhere.