The JB (Jumping Bean) Grenade/XM-197 is a piece of alien technology. It is a grenade that tracks it's target and is highly lethal at close range. It is carried by Black Ops forces regularly, especially later on and tends to start being commonly found around the same time the BBG does. It gets the nickname "Jumping Bean Grenade" from the method in which it operates, namely bouncing off the ground and moving slightly towards any nearby hostiles.
Jumping Bean Upgrade
In the stage Life or Death, there is a small key on a dead soldier in one of the lifts where Cole starts the level. Grab it to open the small lockers in the stage. One of the small lockers in the first power conduit pit has a databank item that upgrades the Jumping Bean Grenade (it now homes in on enemies), thus further increasing it's usefulness in combat.
This weapon is good against Snipers, due to the fact that it flies in a straight line, and can be useful against snipers that the player only knows the general area of, but cannot see.
This can be considered a "Quick Rocket Launcher", as it acts in a similar way to one due to the way the homing system functions.