By your command
"By your command" is arguably the most popular phrase of the "Battlestar Galactica" saga.
By your command spoken by a TOS Centurion
By your command spoken by a Cylon agent
The phrase is frequently said by the robotic soldiers of the Cylon Empire in the Original Series in a neutral metallic voice as the affirmative response to an order from another Cylon Centurion, the Imperious Leader, or other authority.
In the Re-imagined Series, the phrase has been said twice by copies of Number Six, once to a copy of Sharon Valerii in response to finding the escaped Fleet of refugee survivors of the genocidal Cylon attack on the Colonies (Miniseries), and again (barely audible) during the episode "Colonial Day."
Since these Cylon agents appear to run their Cylon fleet as a collective, the use of "By your command" may be less of a command acknowledgement. The use of the phrase may be more analogous to the Colonial affirmation "So say we all", particularly in light of these Cylons' practice of a monothestic religion, complete with commandments.
Note[edit]
A friend of Ron D. Moore, "Roswell" TV series writer Breen Frazier, indicated to Moore that he was surprised that the popular phrase from the Original Series was missing from the early script of the Miniseries. Moore recalled that Breen asked how could the new show be called Battlestar Galactica, without the use of the phrase, "By your command" (Source: The Official Companion).