Suppressor

A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel of a firearm which reduces the amount of noise and flash generated by firing the weapon.

A suppressor is usually a metal cylinder with internal mechanisms to reduce the sound of firing by slowing the escaping propellant gas and sometimes by reducing the velocity of the bullet.

Battlefield 2
In Battlefield 2 suppressors were on the 3 avaliable pistols: the US's 92FS, the MEC's MR-444 and the PLA'S QSZ-92 and were avaliable on the Special Forces Kit and the Sniper Kit.

Battlefield: Bad Company
In Bad Company the suppressed weapons were the Submachine guns and two snipers which were the VSS and SVU.

Battlefield: Bad Company 2
In Battlefield: Bad Company 2 all Engineer class weapons have a silencer including two sniper rifles in the Recon class, the VSS and SVU.

Battlefield 3
It seems in the co-op gameplay video that the pistols were silenced at the start of presentation..

In multiplayer, the sound suppressor attachment can be attached to just about every weapon except shotguns, and will cause minimal damage loss damage at long range.