Most realistic would be Armed Assault, or Operation Flashpoint. Only found in vehicle mounts, selectable rate of fire up to 4,000rpm, damage per round scales as it should for 7.62x51 NATO, accuracy is realistic.
Most fun, for me, was the M134s mounted on the Blackhawks in BF2.
Most fun, for me, was the M134s mounted on the Blackhawks in BF2.