Nothing on the bumpers, but the back window of the truck has a decal that says “WWBD - What would Buffy do?” and a Buddha fish.
I have a “family sticker” on the back with one female adult and 8 cats. I have had people ask “really!???”
No.
MsWhatsit, that is awesome. I would have been smiling all day long.
I used to have two bumper stickers on my little car. The original, “We are all family; we all have value”, was my “take that!” at the Family Values jerks.
The second was an Obama 2008 sticker, from before he picked Biden as his running mate. I felt so hipster, being all pro-Obama before he’d gotten the nomination. Someone ripped it off when I substitute taught at a local high school. Dicks.
Go Beavers! You guys are off to a surprisingly good start this season.
I don’t have any now. I have a magnet for a local University on my car. (I’m on the Board)
To get an idea how old I am, I put a sticker on my first car that said:
I’m a Kentuckian with an “Americans For Nonsmokers’ Rights” sticker on my car (see this thread for why I have it) , so I guess we cancel each other out! 
A magnetic “13.1” oval, because I actually managed to complete a half-marathon earlier this year, and I’m unlikely to ever earn a “26.2” oval. 
I find that runners instantly get it, and most non-runners have no idea what it means, so I suppose it’s kind of a tribal identifier.
I placed a sticker on my actual bumper last year for the first time in eons: Red State, Blue Voter (Tennessee Dem here, although, when my sister in Texas saw it, she asked for and received one 
). Currently, there’s also an Obama 2012 taped on my back window.
Is that an Anita Bryant reference?
Yes. There was an effort to boycott Florida Orange juice when she was its spokesperson. Because of her anti-gay political activities.
No bumper stickers (ever), but I do have a license plate frame that says “Starboard Tack - Stand On Vessel”.
One day I’m going to get pulled over by a police officer who sails and is going to think I’m an aggressive driver.
I am not a bumper sticker fan, but if I had one I’m partial to “Keep honking I’m reloading” or “Horn broken - watch for finger.” I’m not an aggressive driver but I play one on my computer.
Last election season I had a magnetic Obama decal that they sent me for donating. Someone removed it and I haven’t seen it since.
Right now I have a University of Michigan decal on one side window and a Penn decal on the other side window. Because, school. Now that I’m graduated I am considering removing them.
Oh - as for reactions, I’ve been harassed in Columbus, Ohio for my Michigan sticker. They are hard core out there.
Ugh. I hate that this is true, but it is. I know of Michigan fans who have rented cars with out-of-state license plates when they come into town for the football game, specifically so they don’t get harassed or vandalized. People get so stupid about sports in this town.
Currently i just have ones supporting Autism awareness because my son has autism. But back in my younger years I had one that said. Mean people suck, nice people swallow. Yes got quite a few comments over that one.
Just as a random bit of info - research indicates that people who have bumper stickers - of any kind - are more aggressive drivers than people who do not.
I only have three stickers on my actual bumper. It’s unpainted plastic; it’s surprisingly easy to remove stickers from it cleanly. All the other stickers are on glass.
On various locations on my '97 Jeep:
[ul]
[li]2 NC State engineering stickers[/li][li]1 NC State Alumni Association sticker[/li][li]2 lobster stickers[/li][li]4 Maine stickers[/li][li]2 Cool as a Moose stickers[/li][li]a golden retriever rescue sticker[/li][li]a faded 4WD supplier sticker[/li][li]National Geographic window cling (inside)[/li][li]a “ZJ” oval (my Jeep’s model designation)[/li][li]an 8-bit devil rendering (surprisingly cute)[/li][li]“Hurricane evacuation plan: 1) Grab beer. 2) Run like hell.”[/li][li]“Alcohol, Tobacco, Firearms: who’s bringing the chips?”[/li][li]“Not all who wander are lost.”[/li][li]“Cute but kind of evil” (with an Evil Bunny drawing)[/li][/ul]
I have a couple I’m planning to add once others fade or wear out:
[ul]
[li]“I wish Morgan Freeman narrated my life.”[/li][li]“Do what you like, like what you do.”[/li][/ul]
My '09 Jeep only has a few on the back window – a golden retriever rescue sticker, a couple of Maine stickers, a small lobster sticker, and a Cool as a Moose sticker.
Just one-“Kennywood’s open”
“The closer you get the slower I’ll drive”
seems to be working…
I have an EMT sticker on the outside of the rear glass; PD tends to look favorably towards other emergency workers.