According to the site Whole Nine Sports and their draft history for Tom Telesco during his tenure as general manager of the Chargers, the most drafted position for the Bolts has been offensive lineman, with eight picks since 2013.
Those offensive linemen are DJ Fluker (1st rounder), Chris Watt (3rd rounder), Max Tuerk (3rd rounder), Donavon Clark (7th rounder), Forrest Lamp (2nd rounder), Dan Feeney (3rd rounder), Sam Tevi (6th rounder), and Scott Quessenberry (5th rounder).
Of those eight players, three are no longer in the NFL (to add insult to injury, two of those three players – Watt and Tuerk – were third-round picks).