From the sport of paintball, in the form G(number) or if a player were to ask for a G count. The G count is the number of dead opponents. G count is used to keep communication with your team and plan out attacks to close out a game. G counts can range from 1-7 at tournaments but usually a lot more at local fields where G counts are usually off.
(see example 1)

Some times used to pinpoint an actually player as being dead.
(see example 2)