Most states have laws against having stiff dangling from their mirrors-but a lot of people seem to do this. Puerto Rican people seem to favor fuzzy dice (throwback to the 1950’s?), Chinese people like little Chinese lanterns, ans other people like little baby shoes, HS graduation tassels, etc.
What do YOU have dangling from your mirror? 
Some colorful Korean thing that is guaranteed to prevent accidents. It’s worked so far.
Nothing - I don’t need the distraction of motion/sparklies out of the corner of my eye while I drive.
Eons ago (think 1975) I had my high school graduation tassle danging from the mirror of my first car. Then someone stole it - not the car - the tassle! 
Weird.
A little enameled seahorse with a flexible tail.
A hand-carved wooden skull.
I got nothin’. Years ago I hung my tassle from my graduation, but it lasted for about 6 weeks before I got bored with it. Nothing since.
I have a monkey that lno gave me many moons ago. The monkey used to go “EEEEE! EEEEEE! EEEEEE!” when you squeezed it but years in the cold and heat killed my monkey’s squeaker.
I used to have my graduation tassels up but after a couple of years it seemed kind of pointless. I do have Mardi Gras beads, but mostly just because I hang my sunglasses from them. At various times I’ve also had a sparkly blue butterfly decoration thingy, a potpourri sachet, and a suncatcher that one of the kids painted for me when I worked in daycare.
I can’t believe Dopers would do something so dangerous. Having something chronicly moving in the peripheral vision causes one to ignore hazards like pedestrians and cars in the right lane…
Mardi Gras beads here, too – just one strand of extra-nice ones. Although the one we’ve had hanging for the last three years just broke, so we need to go dig out another extra-nice one. I hang the beads multiple times so they doesn’t hang down far enough to obscure my vision, and I choose a strand of non-shiny beads (there is such a thing, although they’re less common).
Papa Tiger also hangs his work badges from his rear view mirror since he tends to lose them otherwise.
I used to have a bundle of blue and gold macaw primary feathers and a freeze dried rattlesnake head on mine. I’ve always had some sort of fetish or statuete for the little kami to inhabit in my vehicle. Now they live in a netsuke next to the sattelite radio reciever.
I’d get my butt handed to me if I did that. Our security office told us specifically that if we’re not in our building or on the grounds, our badges are to be out of sight.
I used to have a few security/parking passes.
Years ago.
A dolphin air freshener (constantly renewed and goes by the name of Snorky) and my university parking pass. Someone at my husband’s law school has a phallic charm though; I always want to break into their car and steal it.
Papa Tiger’s installation is not even theoretically secure; the gates are guarded by rent-a-cops, and rules are enforced by D.C. police. Although, to be honest, I doubt the security concern would even cross his mind; he spent too many years living in Japan, where you can leave valuable possessions anywhere any time and have them be safe and untouched when you return to them. I still have to remind him to lock the house doors at night, for heaven’s sake!
The only thing I ever hang from there is a parking pass for the two high schools I often have to park at. And they’re so small, I can’t even see them from my position.
The Wife hangs a small Christmas ornament of an orange cat with a halo on. She says it’s Ernie (The Best Cat Ever) protecting her wherever she drives.
I don’t recall ever being so distracted by my Hypnotic Skull that I ever overlooked a pedestrian or a car. The only time I’ve ever been in a wreck while my Hypnotic Skull was hanging up had nothing to do with the Hypnotic Skull and everything to do with the car that plowed into me being screened from my view by another car.
I don’t have anything hanging from my rear view mirror, but in the back window (behind my head so I can’t really see it) is a “dashboard monk.” He’s a little Buddhist monk in yellow robes with a happy face who sits on a spring. I like to spread the cheer.
I have an Ebola Virus from Giantmicrobes wrapped round my mirror. It doesn’t affect my peripheral vision, as the rear-view mirror is, at least in my car, in the center of my windshield. As for the peripheral vision, I keep those large convex mirrors on my side mirrors, so I get a very wide field of vision.
Black fuzzy dice. The mirror is high enough that they aren’t blocking my view of the street, though (the extra thick ‘a’ pillars and large mirrors do a fine job of that by themselves).
p.s. I’m not even Puerto Rican!