L3-37

L3-37, known as Leo, is a runaway synth

Background
L3-37 was harbored and memory wiped by the Railroad, having subsequently assumed the name "Leo." The Institute sent many coursers to bring them back, including X9-73, without success.

Appearances
L3-37 is mentioned only in Fallout 4.

Behind the scenes
The designation "L3-37" is a gag reference, as it translates to "elite" in leetspeak, and appropriately describes a synth able to handle multiple coursers without trouble.