It would depend on the case. If the hosts wouldn’t drink it, leaving it behind would just leave them with something they need to store until the next party or find someone to give it to: better take it yourself, letting them know so they don’t go crazy looking for it.
Littlebro is a special case in this respect: he’s the person in his group of friends who’s got more storage space and the only one who lives on his own; the rest have aged parents, children or large pets, so he gets to store anything which will keep from one party to the next. His group also splits around any leftover food if a houseparty was a meal. His cellar is better stocked than many bars, but most of it is things he doesn’t touch.
Taking a couple cans or whatever “for the road” I think is clearly fine.
But taking all your leftovers does make you look pretty cheap.
One of the few benefits of throwing a party is the supply drop.
I’m referring to the truly anonymous undergrad house party here, where people are not expected to know the host and hundreds of randos file in and out through the nigh. I have no idea why you’d host one of these, but a clean house and leftover beer is not one.
Shit yeah…at a byo ‘party’ you take home whatever you brought and didn’t consume.
At a more sophisticated gathering you leave what you don’t drink as an offering for the host to find in the morning and go, BINGO! 
At a dinner party, you bring a bottle of decent wine as an actual gift to the hosts.
Simple.
^Then there’s the type of party where the host wakes up and says, “HEY, where’s the fucking TV?”
Leave the beer. Take the cannoli.
Leave it of course.
Leave it.
I can only think of one exception. Some of my friends enjoy beers that are hard to acquire, released one day a year at the brewery, aged for 3 years, etc. Generally, when I bring a bottle of that type I will have specific people in mind that I intend to share it with. If we don’t get around to drinking it together I’ll take it home with me.
It’s helpful to read these answers. I generally leave beer at parties but am not sure whether that’s the right thing to do or if I’m just cheating myself out of my hard-earned beer out of a hyper sense of etiquette. Sounds like there’s nothing hyper about it.
With food at potlucks, though, I often take leftovers home, because if I don’t, either I make the host stop what they’re doing to transfer the leftovers to a different container, or I inevitably forget to get my container back from the host after the party. Is that rude?
Good question. I say, it’s a completely different calculus, first because the containers, as you say, are normally good reusable ones that the bringer will naturally want to keep (unlike beverage bottles), and second because the contents have usually been partly eaten. Leaving one-quarter of a casserole for somebody isn’t so much a token of your appreciation for their hospitality, it’s more like foisting your dirty dishes on them.
I would leave anything in a disposable container, certainly anything that was storebought. I would generally expect to take my dishes with me, except that if there were any substantial and appetizing quantity left, I’d offer it to the hosts.
If you bring beer to my house, you need to take it with you when you go. That way, I don’t have to find someone to take it off my hands. And generally, I prefer people to take their leftovers home - with only 2 of us living here, too many leftover would go bad before we’d get to them.
I’m not going to encourage you to stop being merciful to these people, but guests who bring their own refreshments to a party where the host has indicated he will be providing refreshments of that kind, are engaging in their own rudeness. That is suggesting that they will find the hospitality of their host wanting. (“Oh, it’s great that Peter is having us over, but he always serves such swill.”)
Recall, the point of hospitality is to enjoy the communal sharing of food, drink, anc conviviality with your hosts and fellow guests, not to ensure that you don’t have to drink second-rate beer.
This is especially true if, at a non-BYOB, one brings beverages for ones own exlcusive consumption. I’d liken it to showing up to a dinner party with Popeye’s. (“I’m sure the vegetable lasagna is delish, but I was just feeling fried chicken tonight!”)
My guess is that this line of thinking is borne out of “Don’t make needless drama and reproach your friends about minor slights” line of thinking. Which is a popular line of thinking. But I think it’s important to recognize that it is possible to (1) not make needless drama while (2) still obliquely telegraphing that certain conduct is not really kosher in order to (3) prevent the “Don’t make needless drama” ethos from degenerating into an anything-goes, lowest-common-denominator license for all manner of tackiness.
It’s funny, I’ve realized my standards vary wildly depending on whether I’m hosting or hosted.
If I’m hosting: please for the love of all you hold sacred take the damn space-hogging things away with you! I don’t care if you take yours, mine, or someone elses’, but at the end of the party weekend, I need my fridge and freezer and kitchen back for their regularly scheduled contents that don’t include me dying of alcohol poisoning in the next week.
If I’m the guest, I don’t think I’ve ever taken my drinks back home with me. Everyone I party with likes to drink more than I do, or doesn’t like to drink what I like, so whenever I head out, I’ll bring something for everyone else and something for me. I obviously don’t want the something for everyone else back, and if I don’t finish the something for me, I know it’ll be in their fridge at the next party because they won’t drink it.
I’m glad that I’ve been so forceful about making people take libations home with them afterparty tho - I’d hate to think what my fridge would look like with all you polite and proper guests!
edit to respond to Kimmy - I think that’s interesting; I’ve never ever been to ANY gathering where the guests didn’t show up with something edible or drinkable for the party as a whole to consume. To NOT do so would be horribly offensive.
If the party is a potluck, then yes, of course, one must bring something. And I get — no (well … only minimal) judgment — that in some places, potlucks are the only kind of entertaining that gets done.
Now of course, I think it isn’t true that you’ve “never ever been to ANY gathering where the guests didn’t show up with something edible or drinkable for the party as a whole to consume.” Even at weddings?
Traditionally, the way to recipocrate invitations to things like dinner parties (or other sub-matrimonial events with food) was to host one of your own and invite your hosts to that.
Over time, with the general lapse of grace and deportment that marks our age, these return invites stopped coming, so hosts began to demand contemporaneous reciprocation. Which is a pity.
Haven’t been to a traditional wedding since I was 12 and had to go because I was a junior bridesmaid.
One friend had a BYOB picnic reception, another had an actual potluck in the church basement, and one did have a reception at a venue, but that one was an alcohol-themed costume party, so most of us brought booze as part of our costumes. 
Dinner parties with my family and friends include people bringing something with them: usually individuals are known for some specialty that they make or can acquire, and are encouraged to bring it to make the party better for everyone.
Some people do bring wine or flowers, but that’s rarer, and even the wine usually gets at least opened during dinner. Food is so much more companionable - it’s something more personal and friendly than flowers or a bottle of wine, and if the point is to share time and interests with people you like - it’s nice to have chances to compliment each other and experience something they made.
I just don’t see a distinction between a “potluck” where everyone brings a covered dish and a “dinner party” where each guest has a small token food or drink to add to the table. I guess what I have trouble with is that I don’t feel that the first is acceptable and the second is rude. I guess all of our dinner parties are actually potlucks after all!
If guests are expected or desired NOT to contribute, then the host usually invites people out to a nice restaurant instead of hosting at home.
that was a total hijack tho - sorry threadpeoples!
I don’t think there’s a problem with a token addition to a shared table.
What Kimmy_Gibbler was addressing was the idea of bringing something that directly replaced something the host was offering, especially for the bringer’s personal use.
If there’s much of what we brought left, we tend to take it home. Unless some member of the host household especially liked it, in which case we leave at least part of it for them. That’s just how the folks we hang with roll, generally. The host provides a bunch of different beers, several people bring a six-pack or two of other beers they like/are in the mood for/want someone at the party to try, everybody drinks freely out of each other’s stuff (sometimes out of each other’s actual beers), and then people take their leftovers home with them.