Two here, both within the last week or two:
One: Wendy’s, apparently hiring for Cclosers, had a sign that read “Now Hiring Losers.” (Hurstbourne LN, Louisville, KY)
Two: Skyline Chili, Bardstown Rd, Louisville, KY: “Ring in the new year with a 3-way.”
When I was in high school, one of my favorite teachers showed me a picture of a Taco Bell sign that read “Now Hiring all Shits.” It might have come from the Internet, and I’m almost positive I’ve seen it somewhere online since, but I’m pretty sure what he showed me was an actual photo. I graduated in 1993, and I don’t think my high school had internet access then.
I think it was a local Dunkin’ Donuts (or some other donut store) that had a sign that read “Now hiring smiling __________ pumpkin muffins!”
I almost applied.
We were sitting in the Country Kitchen having lunch when the Burger King kid next door came out to change the sign. We watched him putting up the letters and tried to guess what the message would be. When he (apparently) finished and went back in, we were still stumped:
HERE’S FOR YOU
A little while later the kid came back out with another person – apparently the manager, who was shaking his finger at the sign and shouting. 
We could pretty much guess what HE was saying.
It came from The National Lampoon Big Book of True Facts, a veritable font of unintentional humor.
My favorite such sign was one I saw in AZ: “Half Baked Chicken.” Somehow it hit my 12-year-old’s funny bone, and I laughed for the whole rest of the vacation.
“My boss told me to change the sign, so I did”
A friend took a picture of a local Captain D’s that was advertising an oh-so-appealing SHRIMP FISH AND CRAP PLATTER one day. If I can find the photo I’ll link to it.
McDonald’s: Try our new McMuff sandwiches!
XJETGIRLX. I don’t quite get it. What’s a “___________pumpkin muffin”?
jackelope, funny stuff! Try to link a photo. 
I"m old. 
There was a space left where presumably another word had been taken off by a prankster. I suspect the sign had said “now hiring smiling faces” followed by a plug for their pumpkin muffins (was up around thanksgiving).
Just thought it was cute, as I imagined little muffin-people roaming about behind the counter.
A friend of mine recently passed the McDonald’s near our office to find that the sign no longer said Big’n’Tasty, but said Big nasty instead.
There was a Black Angus (not fast food, but why not?) that had a sign on one whole side of the building of the name of the restaurant in Neon lights. Seperate lights for each letter, apparantly, because as I was driving by one night I saw
wait for it…
Black An us
It was fixed when I looked the next night.
I suppose this doesn’t really fit as it wasn’t a fast food sign, but there’s a mobile phone store in Cabridge near the Honda dealership. I was getting some clutch work done on my car and I saw it:
“9 11 we will not forge”
:smack: I wonder how long they left it like that!
Dino’s Subs, Arlington Texas:
You can Beat our Prices but you can’t Beat our Meat!
I guess you had to be there…
My last week of work at a local grocery store. I had the responsiblity of posting the “reader board”. I had my helper clerk post - Coke 150_ Bud-799. No one got it
Ain’t seen nothin’ til you’re down on a muffin
Sign in front of a McDonald’s, a couple-three years ago, a sign that was beautiful in its comic simplicity:
NOW HIRING
TEENIE BEANIES
Shortly after 9/11, the Pizza Hut down the street had this on their marquee outside:
God less
America
I thought surely someone would call about it–I didn’t, cuz I thought it was pretty damn funny–and maybe somebody did, but that sign was up there for at least a week.
And the old Burger King next door was demolished down to rubble and dust…but the sign on the marquee, which remained untouched, merely said:
Closed for remodeling
Oh…and during the Christmas season, the Jim’s down the street–kind of a local Denny’s-style place here in S.A.–would put up a different verse of “Santa Claus Is Coming To Town” every week.
But you had to live in the area to know this; I always wondered what passersby thought of the ominous
YOU BETTER WATCH OUT
on the Jim’s sign as they drove by…and then of course, a week later, the different strangers to the area who were confronted with
YOU BETTER NOT CRY!
Since that Jim’s is right in front of a highly-congested intersection, I kind of wondered if maybe people assumed these were thoughtful driving tips.
Not a fast food place, but the Regal Theater near here had on its Now Playing board SCOOBY DON’T. I wish I remembered to take a picture of that.