I’ve noticed a decline in this “art form”, but a few I remember:
“Be like dad, not like sis,
Lift the seat before you piss”
“Those who write on bathroom walls,
Roll their shit in little balls,
And those who read their words of wit,
Get to eat those balls of shit.”
“Here I sit all broken-hearted,
Paid a dime and only farted,
Yesterday I took a chance,
Saved my dime and shit my pants.”
List your favorites!
I used to have a book of bathroom graffiti written in the 60’s. A couple that I remember from the book:
“My mother made me a homosexual.”
and written below
“If I sent her some wool, would she make me one?”
“I wish I was what I was when I wanted to be what I am now.”
On the ass-gasket dispenser in Dallas-Fort Worth airport, no less:
“Free Cowboy hats!”
Back when there were still condom machines in restrooms at gas stations:
" My dad says these don’t work"
“This gum tastes like rubber”
Followed by an inspired bit of not-quite-getting-the-pointism:
“This is a CONDOM machine, yer f*ckin’ DUMASS!” (sic)
Apparently on the tampon dispenser of my wife’s high school:
“Hooray! Free cigars!”
One of my favs.
“In days of old when knights were bold,
And toilet paper hadn’t been invented,
they wiped their ass on blades of grass,
and walked away contented.”
I have also seen full fledged debates on bathroom stall walls before. If you are ever on the George Mason University Campus, check out the West building bathroom-right across from the computer lab.
One that I saw was “For a good time call Susan(insert real phone number all scratched out).” Directly underneath that wa, “HEY! that’s my mom!” It was written very deeply and what looked to be the same pen as the scratching.
“TF4BJ” seems to be fairly common too.
I seem to recall a friend of mine in college had a book of “Grafitti of the Big 10” - a collection of gems from college bathrooms. Many were cerebral and hilarious, and I can’t remember any. So I guess I really don’t have anything to share here…
There was one that always gave me a chuckle. It’s kind of silly (and you probably had to be there…).
Anyway, at one of my favorite pubs, on the lever-action paper towel dispenser in the men’s room, someone wrote:
“RAGE AGAINST THE MACHINE!”
and beneath it, someone else wrote:
“The towel dispenser?”
Just the image of someone filled with righteous fury at the towel dispenser struck me as hilarious.
I saw a list of the top five Linux distributions scrawled on a bathroom wall once. Can’t remember which ones they were, but damn, was that surreal.
“As writing on lavatory walls is done neither for publicity nor personal profit, it must be the purest form of art.
Discuss”
At a highway rest area:
“Here I sit on the pooper,
Just gave birth to a new state trooper.”
I don’t have anything against Texans, but I thought this was interesting when I saw it in a men’s room stall-
“Here I sit, my cheeks a-flexin’
Givin’ birth to another Texan.”
“God saves… but Gretzky scores on the rebound”
above the toilet paper dispenser “another fine abrasive product from 3M”
Above a urinal:
“Don’t look here – the joke is in your hand.”
–Cliffy
Above the pisser:
“Don’t look now, but you have Bill Clinton by the neck and you’re shaking the piss out of him!”
Ain’t that just ducky?
“Never Trust a Man in a Blue Trenchcoat,
Never Drive a Car When You’re Dead”
It’s a quote from the Red Elvises. Amazingly, I didn’t write it, so I find it great.
And now I’m remembering all those wonderul drawing of Ms. Stewart from my days back at the old all boys Catholic School in New Orleans…good times.
Seen on a bathroom wall in a bar, “I f**ked yor mother.”
Below which was written, “Go home dad, you’re drunk.”
I’ve always had a soft spot for good ol’ “Only a child pisses on the floor - be a man and shit on the roof!”
‘The names are the same but the dicks have been changed to protect the innocent.’
I’ve laughed over that for 20 years.
Speaking of the Big Ten, there’s a bathroom at the University of Michigan in which the graffiti consists of lengthy debates – usually either about lesbianism or philosophy, or perhaps both. Though my favorite was the stall with a “What’s your favorite book?” survey. 
(U-M Dopers will probably know the one I mean – it’s the first-floor women’s bathroom in Mason Hall…)
Edith Head gives good costume.
b4i4q ru18? qt (pi). or something like that.
Eric