Team Hot Potato is a team Oddball gametype in Halo: Reach. It is featured in the Team Objective playlist. Hot potato gets its name from the fact that the "oddball" is actually a bomb that goes off (within a yet to be determined time) after being picked up and held.
The bomb goes off with slightly more power than a plasma grenade meaning that defending the bomb carrier too closely can be hazardous to a team's health. After the bomb explodes, falls off the map, or has been left for too long, it will reset and respawn on to one of the bomb "holders" located around the map.