One a white BMW in SoCal
IMJGALT
Ayn Rand would be proud.
GENUIS
Cracked me up for weeks afterward.
Saw this one on a bug in Virginia as well. Laughed my ass off.
Virginia practically gives away its vanity plates, so they’re sickeningly common here. On occasion, I’ll see a remotely clever one:
EVL SMRF (on a shiny blue BMW)
XQQQQME
And one from my adolescence in Ohio that still makes me chuckle when I think of it:
WAS HIS on a beautiful red Mercedes 
OK, I’ll admit it. I just don’t get this one.
Haj
I remember hearing about a guy who, through a confusion on the order form, ended up with vanity plates that said NO TAGS. Which got him confused with every car of the same make and model with no license plates.
I also remember a car in Dallas in the 80’s that said FBI SPY.
A '72 Dk Blue Corvette with ESADMF. We used to say this in junior high, but surprised it got past the DMV and no one ever complained. (Eat S*** and Die MF)
I love when the owner buys a vanity plate that refers to his car and then transfers the plate for a new vehicle. STEVES Z28 on a Thunderbird. MY STANG on a minivan.
(Most likely) Urban legends. Late eighties, Iowa began issuing standard plates beginning with three random letters. Those issued FAG 123, etc. absorbed a lot of vandalism to their cars.
A Chicago man unwittingly chooses two already taken vanity plates. His third choice, NO PLATE, intended to indicate that if he does not get either of his first two choices, he will continue with his non-vanity plate, is accepted. He gets a ticket for every car in Chicago given a parking ticket that has no plate(s).
3M TA3
Eat Me backwards.
Another one I’m shocked got through the censors:
TAX SUX
And one on a physicist’s car:
W LOG K
28 IF on a car at work.
Classy.
It took me a bit to get when I saw it, myself. Trepanning is on operation where they cut a hole in your skull. The car was a convertable. Get it? It’s had a hole cut in its skull!
There was a car I used to see in Champaign, Illinois with handicap plates: BLIND
One of the local ministers: REPENT
Doesn’t that just make you wanna tailgate? HMM?
Former porn star Seka had this on her red sportscar (don’t remember make)
PEN 15. Not an UL, since I saw her get into it.
A guy here in Sweden has a red Porsche with the plates MACHO. Either he’s incredibly good a self irony or a total moron. I hope for the former.
I’ve got one that I’m proud of on my truck. Inside of a Washington Redskins license plate holder is DALASUX.
Here in North Carolina there’s an Odyssey with 2K1SPAC. There’s also a Dodge Shadow with MEANDMY.
My favorite was seeing the car filled with women and a rainbow sticker on the back window. The plate read 2NA (tuna).
That’s what I thought at first but then I thought that I must be missing something more clever than that.
Thanks,
Haj
The Volkswagen Beetle with the “FEATURE” plate is my favorite. I was going to mention it but others beat me to it.
At the time I broke off contact with my father, he was in the process of building up a fleet of toys, and had named them all similarly. The license plate on his Porche 912 Targa said “XNTRIX1.” The back of his sailboat said “XNTRIX2.” I forget what the third vehicle was, maybe a motorcycle. You get the idea, though.
(Not that this matters, but he was able to afford this stuff only by disregarding his divorce-agreement obligation to pay half of my college costs. That’s probably why I have no interest in getting vanity plates myself. I’d rather invent some clever interpretation of the random letters and numbers I’m issued.)
Saw a good one on my way to work this morning : DAMTJM
One of my favorites, seen while visiting friends in Dallas, on an A4 Quattro: “HAUDI” Also, on a Saab Turbo convertible: SNAAB.
License plate frame story: An elderly woman that lived in our neighborhood growing up had a Mercedes 300D sedan, and she also had a 450SL convertible. The license plate frames on both cars was “My other car is a Mercedes.” I wonder if anyone ever explained the concept to her… 
red_dragon60, did you really see that license plate? Which state was that? I always thought that was an UL, kept alive by the call letters on the airplane on the cover of the Beastie Boys’ License to Ill.
Just remembered another good one:
The make of automobile is unimportant, but the plate was just too wonderfully obscure. It said ZVBXRPL. My brother and I stopped and stared at it, and then left an admiring note under the windshield wiper.