Way too personal for this thread, by I still have the shirt that Pasadena (Tx.) Cycle Salvage threw in when I bought the frame for my chopper, nineteen years ago. It’s so worn that I can see the wire hanger through the fabric.
Mine came from the same source and is emblazoned with the slogan (in Purdue Old Gold) Capri Small knows Lady Boiler Basketball! Only a few were printed before Ms. Small (aka the Doper Capri) was issued a cease-and-desist order by Purdue, which claimed trademark infringement. I wear the shirt, but never to Purdue games, as it could theoretically be confiscated on the spot.
home-made tour tie-dyed t-shirt of a graphic of Dylan, Tom Petty & Jerry Garcia riding in a convertible car(I think) for their tour together in '87 or so.
Dylan has a harmonica on, playing guitar, Petty has the tophat and is driving. The words “Don’t tell me this town ain’t got no heart” is around the car.
The back has a wild convertible driven by a skeleton with a bear in the backseat with the words “What a long, strange, trip it’s been”.
Lots of people were looking at me funny as I was walking around today. I was confused till I realized that it was because I was wearing my Circus Contraption t-shirt, which has a picture of an aardvark-headed woman on a trapeze playing a concertina.
I really hope that that was the only reason they were looking at me funny.
I managed to get front row tix for a Stevie Ray Vaughn show. I had a shirt made with big laser-y foil letters, Stevie Ray You Are Soooooooooo Bitchin’ He didn’t look at the crowd much, but he sat on a monitor right in front of us for a couple of slow solos. 
I got my coolest shirt at the little shop at the exit to the Star Tours ride at Walt Disney World. It has the Rebel Alliance symbol (hard to describe: look at the helmets of the rebel fighters in Episode IV; it’s the circle-turned-into-arrows symbol) on the front and says “Rebel Alliance.” On the back is says “Leading the fight for truth and justice.”
“I killed Kenny”
Bought in California, it was hilarious because I wore it when I was with an elderly aunt and she didn’t know why all these young people would walk by, smile and say, “You bastard!” to me.
“Feminist Chicks Dig Me”
The Greatful Dead “dancing bear” in the middle of a rifle scope. Underneath it says, “The Dead Suck”
“Montana. We shoot buffalo because we can’t shoot tourists”
Two regional reference t-shirts:
“If you want to get drunk, go to Trixies. If you want to get bombed, go to Lincoln.”
Lincoln is where the Unabomber lived, Trixies is the next bar down the road (40 miles).
“Whirling disease cures Californians”
Whirling disease infects rainbow trout. Too many Californians come to Montana to fish.
My ECW* crew t shirt. It’s black with “ECF’NW” in red on the front and “You know this means war” in white on the back. It’s the shirt the staff wore and was not available for sale. I got it from a friend who worked on a soundtrack for them. He loathes wrestling and traded it to me for a Northwestern Alumni fleece that I had won in a raffle.
I always get comments when I wear it out. Once at the Columbus airport, a skycap came running over to me asking “where did you get that shirt?” When I told him it was a gift, he offered to buy it from me. I said no and we talked wrestling until my ride showed up. 
*For those who don’t follow sports entertainment, ECW stands for Extreme Championship Wrestling. It was the little federation that only hardcore fans knew about and many of the greatest current performers (Mick Foley, Steve Austin. Chris Benoit, Chris Jericho, Rey Mysterio, Rob Van Dam, etc) worked for them.
Bruce Springsteen Summer 1981 Tour baseball jersey…faded but much-loved.
Warren Zevon: black t-shirt with Old Velvet Nose (the cigarette-smoking skull)
The coolest t-shirt I own is my Beaver Power shirt.
3 favs:
-
BMW Motorcycles: On the front, “BMW Motorcycles” and the BMW logo. On the back “There are more direct ways to work. But I hate my job anyway.” I ride a 1985 K100RS.
-
Thinkgeeks:
> select * from users where clue > 0
0 rows returned -
Got this one in Ireland: “Guiness for Strength”
Below, a picture of an Irish farm worker pulling a wagon, with the dray horse inside the wagon.
I made up a t-shirt for Dorm orientation one year, it’s hot pink with black text:
A Boundless Supply
Of Help, Knowledge and Wisdom
Lies under this stylish and
instantly recognisable t-shirt
Go ahead, ask! I wont’ bite!
usually
But my favorite isn’t a t-shirt, it’s a cap, a Bubba Gump Shrimp Co. cap.
I like my “MapKnap – Help us make a point!” t-shirt.
It was from a Knap-in* and atlatl throw at Moundville Archeological Park in Alabama.
*Knap-in – where folks (mostly guys) sit around and practice making stone arrowheads by flintknapping. Very cool. Some of those guys would be very at home in the Paleolithic era. Me, I’m good at making smaller rocks out of bigger rocks.
“Blessed am small rocks. Guys make 'em from bigger rocks.” -Book of Og, Chapter VII
actually, the formula statement is “SELECT * FROM users WHERE clue = TRUE;”
i’ve seen that in ComputerGears catalog, and am dying to get one for myself (since it’s one of the few SQL-based geek shirts i’ve ever seen. and after working HelpDesk for awhile, it’s definitely a True Statement.)
currently owned favs:
black with hand-written style white letters: Don’t annoy the crazy person.
khaki green with white letters: I haven’t been the same since that house fell on my sister.
haven’t found just the right venue to wear it yet, so the background color is not registering; but the lettering is black, with a picture of Stonehenge and various peoples dancing in front of it, apparently going in a circle completely around it. the text: Give me that old-time religion.
most, if not all of these, were gifts from my husband. i’m not quite sure what the overall message is… or exactly to whom it is addressed.
“All the good paying jobs start before I wake up”
I used to take pride in wearing that shirt when I was a work-from-home web designer for a computer consulting firm
It’d have to be my AJ Hackett bungy jump shirt. I earned that baby.
I have a T-shirt from the Broadway on Broadway free outdoor concert held on September 9, 2001. Sometimes I just look at it and think about going into and out of NYC on the bus that day, and not once even noticing the World Trade Towers…
I don’t own this one yet, but my uncle just saw it and I’ve told him to buy, beg, borrow or steal it for me:
“Somewhere in Texas there’s a village that’s missing its idiot”
Just got this one from T-Shirt Hell:
“I’m what Willis was talkin’ 'bout”
Now it’s my favorite.