A Dead Weight Card is an uncommon but notable form of card. Its only purpose is to clog up someone's hand.
The basic form of this is a card that cannot be played, but there are other types too. Cards which can only be played under a nuttily specific range of circumstances often become this. Under certain variants of the game, or under certain Rule Cards, it is possible for Useless Cards to be this. Of course, this also covers cards which inflict penalties on whoever plays them—compare with Creeper Card, which causes bad effects as soon as it's drawn.