"Real Sluts Don't Use Condoms" for a t-shirt...
could be a series too where the guy starts to get one and the girl says that line and then they start going at it really seriously

"Geeks Make Me Wet, But Loosers Make Me The Wettest....." for a t-shirt
In the video the tramp will get not quite bangbanged by a group of worthless, limp-dicked posters from the other 'bored'.

" If you think im a dumbass , you should meet Sir Noel Plum " for a t-shirt .
In the video you could show monkey's throwing feces at each other .

How about a childrens line of shirts?
"ARE YOU MY DADDY?"
"MOMMY IS A CRACK WHORE"
"THEY SHAKE ME"
"THIS BABY BROUGHT TO YOU BY BUDWEISER"
"I'LL BREAST FEED WHERE EVER I LIKE!"

I think some of those were done already Phatboy.

My cousin got one for her son that says "Got Breast Milk?".

Of course there's always, "Who's my daddy?"

How about... "My mom is easy"
"My mom is a slut"
or "My mom is a whore"