I can’t give a cite, but I’m almost 100% certain that this gets said at least once over the 9 seasons of the show.
The IMDB says it happened in “Paper Clip.” Season 3, episode 2.
According to the transcripts available online, he said, “I’m more certain than ever that the truth is in there.”
Sorry to reanimate the dead, but I just wanted to defend my earlier assertion with an actual cite now that I have one, and also because I’m liable to remember later that I came up with a cite but forget what it was. 
Both Mulder and Scully say the phrase “the truth is out there” during season one of The X-Files.
I’m glad this thread was resurrected. It brought to mind the classic sign on the wall in “2001: A Space Odyssey:”
ZERO GRAVITY TOILET
PASSENGERS ARE ADVISED TO
READ INSTRUCTIONS BEFORE USE
IIRC, the actual slogan for Strategic Air Command during part of the Cold War.
Don’t recall if it was in Serenity, but in the TV show Firefly, “Blue Sun” might count. We see the logo for this company (with the company’s name in both English and Mandarin) printed on damn near everything, including a main character’s t-shirt, yet it is never commented on, evidently being as omnipresent as Kraft Foods.
“VOTE FOR PEDRO”
Or was that spoken?
Was “All work and no play makes Jack a dull boy.” spoken?
From Animal House: “Knowledge Is Good.”
nvm
I don’t believe so, simply written 1000 times:p
“Wake up, Neo”
Welcom to Denton, the home of Happyness
The first one I thought of:
NOW I HAVE A MACHINE GUN TOO HO HO
In 1997, there were two movies about a volcanic eruption in California. One was called Dante’s Peak and the second was boringly called Volcano. As I remember, both were awful. But at least Volcano had the tagline, “The Coast is Toast.”
I’m confused by this. The line is “Now I have a machine gun. Ho-ho-ho,” and it is most certainly spoken. Hans reads it out loud off the shirt John wrote it on while standing in the elevator. Are you saying that people often misquote it?