The act of throwing a hail mary grenade pass at the surviving teammate of a Hot Potato at the start of a Halo Reach match on Xbox Live while saying "and he goes for the hail mary!" on the headset piece. Originating in Jan 2011 in North Alabama, this move has pissed off thousands who play Halo Reach. 80% of the time this move works and the targeted teammate is killed. If the 4th teammate is still alive then the hunt and quest begins for killing him. This hunting scenario is called the Halo Rabbit Hunt. Please refer to Hot Potato for events leading up to the Hot Potato Halo Mary to better understand the process which takes place.
That dood survived the hot potato but I got him with the Hot Potato Halo Mary!