Shelfwarmer

Shelfwarmer is a colloquial term for a toy that fails to sell well, leaving residual quantities on store shelves for months or even years after its original release, generally far in excess of other toys from the same waves.

A related term is pegwarmer, used to refer to toys packaged on cards (which thereby hang on pegs), rather than in boxes.

From Teletraan I: The Transformers Wiki, a Wikia wiki.