Shelfwarmer

Shelfwarmer is a colloquial term for a toy that either fails to sell well or is over-produced, 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.