I would have to say that the replicator technology is my favorite based on sheer convenience. I would also contend that it is the most influential piece of technology on civilization in the Star Trek universe. The replicators initiated not only a technological revolution, but an economical one as well. With the widespread use of replicators came an era of prosperity and a quality of life never seen before on Earth.
Capt. Picard: This is the 24th century. Material needs no longer exist.
Ralph Oppenhouse: Then what’s the challenge?
Capt. Picard: The challenge, Mr. Oppenhouse, is to improve yourself – to enrich yourself. Enjoy it.