The Frigate is an excellent all round frontline ship capable of holding its own against the creeper.
The Frigate serves a similar purpose as the Gunship, capable of dealing immense damage to the creeper using its Mercury Rocket Launchers. In addition, it is able to hold its own without needing support from other ships thanks to the three Mark 1 Cannons.
Don't tell O.D.N. that I told you this, but I heard some commanders say that they park this ship backwards towards the creeper to enhance the range of the rocket launchers.