Lugia
Lugia has fantastic HP, Defense and Special Defense at 106, 130 and 152 respectively. It also can have Multiscale at it's Ability, which reduces the damage Lugia takes when its HP is full. Lugia also has access to recovery moves such as Roost and Recover, and can learn Toxic and Thunder Wave. Though a great wall Lugia can't really hit all that hard so won't cause "great damage", unless it has a lot of EV investment in Special Attack or Calm Mind. Many people will say go with Aeroblast for your attacking move, however I personally would suggest giving Lugia Ice Beam, as it's super effective against much more Pokémon in the Uber's tier than Aeroblast is.
Giratina
Giratina like Lugia has fantastic HP, Defense and Special Defense at 150, 120 and 120 respectively. Even though it can't learn Roost or Recover, it can learn Rest which is completely viable on Giratina along with either a Chesto Berry or Sleep Talk. It has access to Will-O-Wisp, Thunder Wave and Toxic and can deal decent damage depending on the EV Spread with moves such as Shadow Ball, Dragon Pulse and Aura Sphere.
Arceus-Ghost
This Pokémon without a doubt deserves to be included on this list, it has fantastic HP, Defense and Special Defense at 120 in each Stat respectively. It has access to Recover and Will-O-Wisp, and after a couple Calm Mind it will hit neutral targets hard with STAB Judgment!
