This is probably one of the strangest, yet coolest seed found so far in minecraft. It features a stronghold floating in the ocean, and inside the stronghold is a portal room with a mob spawner.
Not only that, but the seed also has an NPC village on an island right next to the stronghold. This is a very rare seed, and it also works for multiple versions of minecraft.
Stonghold coordinates: x: -534 y: 57 z: -833
This seed works for minecraft version: 1.2, 1.3, 1.4, 1.5