dump horse 

A responsibility which really should be somebody else's, but which has been "offered" to you as an "opportunity" in a way that you can't refuse, effectively dumping their responsibility on you but pretending that it's for your benefit. The difference between a standard dump and a dump horse, however, is that -- despite the total lack of altruism on the part of the dumper -- the dump horse actually does benefit you, and you truly can turn it into an opportunity.

"This presentation was supposed to be Joe's, not mine, but it gives me the opportunity to really shine in front of the CEO, so I won't look a dump horse in the mouth."

dump horse by ArsCerebri December 3, 2013