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.
The XM-197 can be upgraded to home/lock onto it's targets , thus further increasing it's usefulness in combat.