Moved to WEHZ.
No idea what you mean by an attack ability.
You can make an attack like a machienegun by removing the damagepoint on a unit's attack (setting to 0) and then setting its period/cooldown/attackrate (whatever it is called) to 0.01 (do not set to 0 as it will cause the game to lock up). It will then attack 16 or so times a second which might not be the 100 rounds a second of some machieneguns but it is still insanly fast.