Spear Gun

Speargun was a cut weapon in Battlefield 2 Special Forces.

The weapon was cut in very early version of BF2SF.

Spear Gun was most likely used to shoot enemies underwater, since there are no underwater levels the Spear Gun would be useless.

Source
http://www.bf-games.net/readcontent/60/battlefield_2_special_forces_waffen.html (In German)