I know that NF already has the Baram Class "Monster" ship and the super H44 class "Beast" ship, but I had a few suggestions that would allow TNF to hold more events like this without using the same ships over and over again.
1. A super heavy battleship/carrier hybrid with the ability to hold a tremendous amount of aircraft. For armaments, I would suggest the Yamato's x3 18.1"/45 caliber type 94 L for the main armaments, and a gun with the range of the French x2 3.5"/50 cal model 1929 and the fire rate of the Italian x1 3"/50 cal model 1909. Due to its size and weight, the speed should be similar to a fully armored Queen Victoria, and the armor to match. For aircraft, what better to equip a ship like this than with Japanese Aircraft. A ship like this could receive massive income because of its massive destructive capabilities.
2. A large submarine equipped with decent sized guns, super heavy torpedoes, and an incredibly high air supply to allow for very long dives.
3. A battleship type with the ability to shoot down aircraft before being spotted. Something like this would force players to use other tactics to find this craft.