We always called those suicide knobs.
Yeah, all that crap is still available. It’s just moved to ebay now. :rolleyes:
I actually considered getting one of those steering knobs a couple of years back when I broke a bone in my wrist and had a cast, but in the end I managed to steer just with my fingers. Probably not the safest thing, but it worked.
Every Lincoln Town Car my grandparents owned had a big ol’ floating ball type compass mounted on the dash.
“Necker knobs” have been illegal since at least the 1950s in m ost states, and probably all since… well, Alabama… 2000. 
My favorite was from the early 90s, where they advertised some kind of a bypass valve you could get plumbed into your exhaust to bypass the muffler and catalytic converter to get better gas mileage on the highway.
Even then, that got the raised eyebrow… :dubious:
The first car my mother drove (in the early 60s) didn’t have a radio at all. She bought a transistor radio, and a set of portable “speakers” for the car: the speakers were essentially one small speaker on either end of a cardboard tube (imagine a Pringles can with a speaker on each end), with room inside the tube for a couple of D-cell batteries, and a wire which connected to the earphone jack of the radio. When I was a kid (1970s), we still had the speakers, and I used them with my own transistor radio.
Jcwhitney still lives in the net. Check it out.
Back in the 90s I had plastic wind deflectors that stuck above your windows so you could just crack them open and get air but not get wind in your face.
Also great for smokers since the ashes would go out of the car and not fly back into the back seat.
These are very common elsewhere in the world.
I got a wink? mirror once. Basically it was a rear view mirror that was like 3 feet long give or take.
Man could you see everything with that baby. So much in fact it was rather distracting for a few months till I got used to it.
Good job I don’t live in the States, then. 
AFAIK, they’re still legal in the UK - although it’s a bit of a grey area. Like I said, I didn’t bother in the end - would probably have just gouged the leather on my wheel.
I think we put an aftermarket cruise control on one of our cars in the 70’s. I don’t think it ever was reliable enough to keep you at a constant speed.
My older sister’s boyfriend in the mid 60s had an under-dash record player.
I had an FM converter, then later an under-dash Pioneer ‘Supertuner’ FM/cassette stereo that I removed and took with me whenever I left the car.
I also installed a tachometer on the steering wheel column. Dad asked me why. I said it looked cool. He said I should have spent the money on a haircut instead. Did I mention it was installed in a Gremlin?
mmm
Pedal covers that looked like feet.
Little fans that mounted on the dash.
Motorized radio antennae.
Wooden and plastic shifter knobs with various designs.
Sportier side-view mirrors (this was before power mirrors)
Spoilers to mount under the front bumper. I bought one and, like an idiot, painted it before seeing if it fit. Of course it didn’t.
How about louvers?
Or those sticker tints placed at the top of the windshield with various messages or manufacturer logo.
When I was a young’un, driving used cars that I never paid more than $1000 for, getting loud music in them was a priority. I have had under-dash 8-tracks, cassette players, and equalizer/amps hanging down in the past. I have built big wood speaker boxes to fit two pairs of 6x9" coaxial speakers for the back of a Vega station wagon. Even though none of this stuff was really top-end, I did come up with some combinations that sounded great.
Other stuff I had over the years:
Stick-on rear window defroster in a '66 VW. Worked great. I also put in a two-dollar interior light under the dash.
A corded cigarette lighter that plugged into the lighter socket. The lighter part hung from a clip on the plug and was attached with a telephone-like spiral cord. To use it, you picked up the lighter end, stuck your cigarette in the hole, and pushed the button. It was instant, no waiting for the pop-out kind.
I put a cruise control on a '78 Chevette. Worked fine on flat roads, but the 'vette would lose too much speed going uphill, and it would shut off.
I put fog lights on one car, and ordered seat covers made specifically for it from J.C. Whitney. They were exactly as advertised, and a fine value.
These may not really be accessories, but I ran retreads on my first four cars (back in '78-84). The fourth got a set of radial retreads! Never had a problem with them. Tried them on my fifth car- it was disastrous. Never bought any since.
The second time our Mustang was stolen, it was recovered the next day with the chrome “foot” gas pedal stolen and the almost-new lace-on wheel cover mostly unlaced.
I am reminded of the Woody Allen scene where he runs away with the piece of glass from the jewelry store window…
I had an uncle who was in the UAW and “knew something about cars”.
One gadget I especially remember were small “wings” that he attached to the posts on either side of the rear window of his station wagon. Looked kind of scary. They were supposed to keep the dust from sticking to the rear window, keeping it clearer. Sure, why not.
(That station wagon had an engine fire and was totaled. So he took it to the mechanics class in his building. They completely restored it as part of their training. Got it back better than before. He drove that thing for years. Rare in those days. Still with the dust things.)
Ah, found a pic, but my uncle’s car was older.
One common accessory when I was real little was one of those burlap covered water bags hanging off the hood ornament in front of the radiator.
My (beloved and missed, really) '68 Merc wagon had those built into the body styling - side/corner scoops. You can see them here.
I can’t say that they did much of anything.