Joe

"Report to One-Eyed Joe in the stables."

- Maester Aemon to Luke Joe, nicknamed One-Eyed Joe, is an unseen character in Game of Thrones. He is a member of the Night's Watch, and apparently chief among the stewards stationed in the stables at Castle Black.

Season 1
When the newly graduated recruits are assigned to their orders Luke is told by Maester Aemon to report to One-Eyed Joe in the stables.

In the books
In the A Song of Ice and Fire novels, there's no member of the Night's Watch called One-Eyed Joe.