The Night Empress. The last word in Night Battle ARs (though 9A-91 gets close with her unique). Also somewhat usable during the day (G41 tier), but having +200% damage at night allows her to even do some damage to armor despite being an AR.

That said, with armour increasing dramatically in future events, most likely not worth duping. By Singularity, and especially later, armour will have increased to the point of making even low-tier rifles much better than ARs.

The Night Princess. If you need a Night Battle AR, she's the 2nd best girl behind Groza. Unlike Groza, you can actually build her. Her unique equip makes her even sillier, but she's excellent even without it… at night. At day, she only barely keeps up with FNC or F2000.