Guess you can't be serious in this community.
A light-hearted name can be a serious suggestion for a fun game, I guess you meant a serious sounding name.
It would help if we knew more about your game other than "top down shooter"
What's the setting? Medieval Fortress, Old West, Modern Urban, Futuristic Spacecraft?
Who are the enemies? Zombies, Cowboys, Terrorists, Aliens?
Medieval Fortress + Zombies = Fortress of the Damned
Old West + Cowboys = High Noon Showdown
Modern Urban + Terrorists = Critical Mission
Futuristic Spacecraft + Aliens = Xenoblaster