Often times, when filling out (non-government-related) forms, I’ve listed my occupation as “Student of Life”.
Anyhoo…
The railroad has a few good ones:
Roadmaster
Trainmaster
Yardmaster
And derailment contractors have Wreckmasters
While working on the development of an RPG, I was the only one who kept all the (constant) rules revisions in my head, and quickly earned the title “Rules Monkey Overlord”. I shoulda had business cards.
My buddy worked at a grocery store once loading groceries for the lazy slobs who cannot do it themselves; his position was titled “Rear-End Packer.”
I was a Stud Man for General Motors.
Supreme Allied Commander. Gimme a job title with “supreme” in it, any day. Lucky Wesley Clark.
I am Vice President in Charge of Crayoning. Got a business card and everything.
On the old show What’s My Line they once had a sagger-maker’s bottom knocker
He made pots, apparently.
At one point, my office had two clients whose real-life titles were, respectively, Condom Manager and Lubricant Supervisor. Too bad they worked for different companies; staff meetings might have gotten rather interesting. 
Dad was an engineer on rocket boosters at Martin-Marrietta (looong time ago). He took great pride in his business card job title reading:
“Rocket Scientist” 
Cheers,
Vega
The official listing of occupations once used by our government department had a listing for “Gunner”, which was job title for the guy who operated the machine which produced “XXX, the cereal shot from a gun!” (Puffed Rice?)