"I would never lie. I willfully participated in a campaign of misinformation"
This is actually one of my favorite Mulderisms. Mulder was rather un-punklike for a change. I have very little to complain about. "Shadows" is the first episode where someone actually requests his input. (Colton in "Tooms" doesn't count.) Amazingly enough, Mulder doesn't seem interested.
Mouthing off to people he believes to be NSA, CIA, or someone else of grand importance. Probably not the best move. Even if one isn't inclined to want to impress them. People like that can make one's life a living hell if one pisses them off.
Barging into Lauren's house. Okay so maybe it's part of his job, but I just hate it when authority figures just push their way into people's homes when the person in question clearly doesn't want the company when said person isn't under arrest.
Impeding an investigation: Tsk! Tsk! Not the way to keep your division open Mulder.