Driving through an oh-so-classy area of Bloxwich
I got pulled over by a young lady copper who was quite sweet, if a little officious. As she was going through my paperwork and taking down my particulars she caught sight of the T-shirt I was wearing - beneath my unzipped hoodie and the seatbelt she could quite clearly see the image of a jolly policeman, beneath which was some writing that she wouldn't have been able to make out.

With that all friendliness dropped from her demeanour and she asked me to step out of the car so she could get a better look at it. Then she said "Wait here" and turned to the meatwagon parked a few yards up the road. After a quick conversation at the window, the doors opened and six or seven burly male coppers (presumably her back-up) got out.

"See," she was saying. "I told you you had to see this."

And so it was that I found myself standing by my car in a rough, debris-strewn part of town while the police stood in a line, pointing and laughing at my T-shirt. They asked me where I got it. "Viz", I replied. It was an enlargement of one of their adverts that read:
MUGGED? BURGLED? RUN OVER?
WHY NOT CALL THE POLICE?
THE POLICE: TEL 999

After they had finished laughing, they started talking amongst themselves, apparently forgetting I was there. After what seemed like an eternity - I was certainly drawing looks from passers-by at this point - I raised my hand and asked in a deliberately meek voice: "Can I go now?"

The young lady copper was all smiles again and even apologised as she sent me on my way, but I still wonder how the whole thing might have turned out if they hadn't had a sense of humour about it. Also, I was younger back then (obviously) and regularly wore a selection of "dubious" T-shirts but as a result of this encounter I became a lot more circumspect in what I wear; the marijuana-leaf PWEI shirt now only comes out at hippy festivals, for example, though annoyingly I've not got any more circumspect about buying them. Christ only knows when I'm going to get the chance to wear my Kunt and the Gang "FUCKSTICKS MOTHER'S CUNT FUCKSTICKS" shirt without getting nicked by the first copper to clap eyes on it :/
( emvee cruor deo cruoris, Fri 6 May 2011, 7:54, 2 replies)

Yes, I have a shirt like that
It's a Tintin cartoon, where a drunken, unshaved Tintin is buggering Snowy the dog. I bought it a Pride, and have since discovered that there are very, very few occasions where it's possible to get away with it.
(moon monkey is busy making memories worth repressing, Fri 6 May 2011, 10:18, closed)

My pro-necrophilia t-shirt...
...is slightly more subtle, but still one I'm circumspect about wearing.

The most epically stupid t-shirt fail, however, was the time I went through Chinese airport security forgetting that I was wearing a Dalai Lama t-shirt.
(stalinism, Sat 7 May 2011, 14:35, closed)