"Victory attained by violence is tantamount to a defeat, for it is momentary." - Mahatma Gandhi.
This character is third in command after the ship's Commanding Officer & it's First Officer. He/she is responsible for assisting in the command of the ship during the story and overseeing the SIM in the CO and XO's absence. The Second Officer should be the right hand man to the First Officer and capable of stepping in to oversee the SIM. The qualities that make a good CO & XO, apply for this position as well. Second Officers are selected by the CO of the particular ship.
The 2O plays mainly on the bridge, but like the CO and XO, can be moved all throughout the ship and on most of away missions.
Examples from Star Trek are Mr. Data and Cmdr. Trip Tucker.
This is a command position that is heavily featured in nearly all missions and will see many opportunities for activity.