nay. By the time I was 20 I had outgrown the need to broadcast my opinions to people who don’t care what I think anyway.
I have a Subaru. So by law, I have to have at least one bumper sticker. 
One is an Obama sticker. Yeah, I know I should remove it, but I don’t wanna. I have a “Virginia is for Lovers” sticker and a “I Live in the Chesapeake Bay Watershed” sticker. Am I really passionate about Virginia and the Bay? Not really. But I work on behalf of both, so I kinda feel obligated to give a shout-out.
I don’t dig aggressive or offensive messages. There is enough road rage as it is. What I really hate are bumper stickers that have such teeny tiny print that you have to be almost right on the bumper to read it. That just doesn’t make any sense to me.
Greatful Dead bears. I like the music, and it’s a great graphic.
I have had only one car that I apply(ed) any stickers to. It is an old 1970s Ford van with tan-ish peeling paint. It came with about 20 humorous stickers and lots of dents.
As the paint peels (with or without) any applied stickers, I lightly sand and primer the area. I then paint it with another shade of tan (can not find the original). After about seven days, I apply another humorous sticker or three.
This gives the folks behind/beside me on the road something to laugh at. If I see someone laughing I ASSuME that they like at least one of my stickers. I often find a small croud gathered around it laughing when I go to gather it up from some parking lot.
BTW my stickers all are LARGE PRINT.
FWIW, Any stickers on any of my other rigs are from the PO. PO=Previous Owner. I only remove the offensive ones. Pissing kid, saying someone/thing sucks, is an A-h…, you get the idea.
The oldest one I have is a Presidentual Physical Fittness award/seal on my 1959 Ford pick-up. I have seen photos of this PU with this seal that were taken in 1962. It is on the lower left of the windscreen. I hope I never need a new windscreen. otherwise I would try to save that seal. Obviously this seal was awarded to the truck and I am proud of the truck for it. It stays!
I once had a bumpersticker on my car that read:
Does This Offend You?
Image of a punk mooning the viewer
GOOD!
I found it particularly apt; if it offended you, good, if you’re intolerant enough to be offended by it, you deserve to be offended by it. If not… good! You’re the kind of person I like!
I somehow doubt anyone got the intent, of course.
This covers it. I’ve never changed my mind because of a bumper sticker (or yard sign, or t-shirt, or demonstration, or…). No matter what my beliefs, I doubt if random people on the highway will suddenly convert to my opinions.
Other than required stickers for registration, parking and barcodes to open gates, my vehicle is sticker-free.
Looking around the garage, my eldest’s car has school bumper sticker, and a Whiskey Tango Foxtrot label (?). My youngest’s car has only school parking permits (odd, she’s the most vocally, and politically opinionated). My wife’s has an old “NameOfSchool Honor Student” sticker. The RV has a small oval sticker from our favorite state park (I have no idea why I put it there). Nothing on the boat or motorcycle other than reg numbers, and the UTV has only a TX OHV permit. It *does *however have brass balls hanging from its trailer hitch, but I’m doing it ironically so it’s OK. 
I love my current car and would never even dream of putting a bumper sticker on it. But, the previous car I had but one had been in an accident. A friend had hammered down the trunk to be as flat as it could but it was still clearly damaged, and very ugly. I put bumper stickers on the entire bumper of that car. It looked ugly anyway, and at least the bumper stickers provided something different.
I have lots of stickers! On the '09, I’ve limited it to four on the back window. I have three actual bumper stickers on the '97…however, my bumper is unpainted plastic, and even old stickers are very easy to remove. The '97 also has plenty on the back window. Some are humorous:
[ul]
[li]“Alcohol, Tobacco, Firearms: Who’s Bringing the Chips?”[/li][li]“Hurricane Evacuation Plan: Grab Beer; Run Like Hell”[/li][li]“I wish Morgan Freeman narrated my life.”[/li][li]“Tesla > Edison”[/li][/ul]
Others are related to travel destinations, favorite stores, or just good old bumper school philosophy (“Do what you like, like what you do” and so forth). I remove the stickers when they become tattered or faded.
I checked “I don’t have any bumper stickers” and “Other.”
My current car doesn’t have any. I had one on my last car, it was an Obama/Biden '08 sticker.
I may put a U. Cincinnati law sticker on my 'speed 3, but only on the glass where it can be easily removed.
Three weeks ago I was behind a Cadillac with Manitoba plates sporting a Vote Bush bumper sticker.
Some mothers have 'em.
I have on that says Kennywood. I like Kennywood.
My SO has not only a Purple Heart license plate, but a 101st Airborne Screaming Eagle on his rear window (pickup truck). He tells me he’s avoided tickets that way. And yes, he has a Purple Heart.
The only one I have is the Human Rights Campaign “=”.
I have one of my favorite sports team logo. It comes in handy because I have a very common make and model of car and it helps me find the car in a large parking lot.
I am of two minds about the COEXIST stickers, one hand it is nice of the idiots to label themselves, but on the other hand it is depressing to know there are so many.
They can be very useful in identifying and avoiding The Crazy.
For most of my car owning life I’ve driven without stickers. The few I’ve ever affixed to a bumper (rather than the inside of my high school locker or the outside of a dorm fridge) have been for my son’s schools; elementary and middle. I’ve never gotten one for his high school.
I enjoy reading other people’s stickers.
I have one sticker I have to have to prove I live where I live. Right now, the other two are “Cultivate Peace” from thehungersite.org because if just one person clicks per day because of it, it would all be worth it…and a white oval with pretty pink letters saying “Quilters do it in the ditch”.
Former favorites included “Don’t be sexist. Chicks hate that.” and “Honk if you love peace and quiet”.
I think they’re tacky. I got tired of seeing all the Obama bumper stickers around so I got an anti-Obama one and a Gadsden flag for good measure, but they fell off my car (I didn’t want to stick them to the paint so I got magnetic backing) and I didn’t replace them.
I have several: a 13.1 oval and an Oregon heart on one side (saving space for the 26.2). On the other side are three outdoor brands that I like: Keen, Mountain Hardwear and Marmot. I used to have an REI license plate frame and my plate has a cyclist on it and reads “Share the road”. My car just advertises what I like to do when I’m not working. I feel it attracts the kind of people I’d be interested in hanging out with. I might put more on in the future. I’m looking for a good cycling one and I’ll probably put a hiker on there at some point. Mine are all outdoorsy. I’d probably be inclined to do environmental, but not political or religious.
Dutch Bros. (drive-thru coffee shops) seems to be all the rage here. Just about every car has one. Mine will not. I like coffee, but I haven’t found a shop I’m willing to shill for on my car.
I have one now, as I usually do; my bumper sticker is almost always political. I change it every election cycle for whichever candidate I most strongly support. In any Presidential or gubernatorial election year, it’s almost invariably going to be the Democratic nominee’s.
I always read others’ bumper stickers in traffic. I often see a particular car on my morning commute with, I think, six bumper stickers (all political and/or ideological). That’d be too many for my tastes, but I enjoy seeing them on others’ cars.
I’m amazed to still see, every week or so, bumper stickers from the 2004 Kerry/Edwards ticket, even now. I think, Dude, that was two election cycles ago, and the ticket wasn’t all that… take it off!