I found this replicator on Oct. 25, 2001. It repeats every 11 generations, on a one-dimensional 4-unit grid.
This rule has only one known spaceship. It is unknown whether the replicator can lead to high-period oscillators, spaceships, guns, or other interesting technology.
Replicators -- Cellular Automata -- D. Eppstein -- UCI Inf. & Comp. Sci.