You show up to a party with a sixpack/twelvepack/case of beer. Is it rude to take the leftovers home with you? What if it’s expensive beer?
Full-fledged party? Grab it on the way out.
Smaller gathering, where it might also be appropriate to bring a bottle of wine? Leave it.
I’m more likely to leave a good beer.
Don’t bring what you’re not willing to either consume or leave behind.
I agree with Sicks Ate. Traditionally, if you bring something with you to a gathering, you’re essentially bringing it as a gift to the host. But if you’re at a big blow-out, it’s more likely that you’re just making sure there’ll be enough for you.
Do they sell expensive beer in twelve-packs?
Expensive, or good? A 12-pack of the seasonal variety from Boulevard Brewing is a default pick for me. I’m a fan of variety packs, so substitute Boulevard with Big Sky, Sam Adams, Blue Moon etc.
As a party goer, it wouldn’t even occur to me that it was rude to grab your own beer on the way out. This assumes it’s a BYOB party. Different story if you’re the guy that agreed to supply the beer for the party.
As a host, take your beer with you please. I don’t want your crappy beer crowding my fridge! 
Sicks Ate has it. Two caveats: I’ll take beer home from a smaller gathering, with the host’s permission, if I know that the host doesn’t drink beer and only asked people to bring it to make sure that it would be there for guests. Also, at very informal events, where I brought beer mostly for myself even if I did give a couple away, I’ll take it home.
Which reminds me…if I take cider, there won’t be any left to take home. I’m a sucker for cider.
Another good point you make..it depends on the host. There are places I go where, if I bring ‘good’ beer, I might was well take it back home with me. Miller Lite is the drink of choice there.
I always bring more than I think I’m going to drink, and leave the leftovers. If I’m going to be at a party for the majority of the night, and I expect to drink 8 - 10 beers, I’ll bring an 18 pack of a popular macro-brew that I like. Or maybe a six pack of an independent that I can share, and a 12er of a popular beer. That way if anyone else runs out, they can have one of mine instead of having to make a run.
This only applies to beer however. If I feel like drinking gin and tonics or vodka martinis and I have to bring the hooch to pour my drinks, I’m taking the bottle home with me. Does not apply to wine.
The parties I usually attend “leftover” doesn’t occur.
It’s a gift. You shouldn’t take back a gift. However, I can see a lot of circumstances where there’s nothing wrong with asking the host if you could take some beer home with you.
Store-bought, sure.
Home brew, I’m taking whatever’s left, and the empties, too.
Take it, but strain out the cigarette butts first.
I’m thinking the OP is talking Sam Adams not Trappist, expensive compared to PBR. Certainly there is “good” stuff in 12 packs, and I hope none of you think that if someone only drinks Chimay that means they’re gauche proletarians.
That runs the risk of wanting to drink but being out, then you gotta mooch some more or be sober, two equally disquieting situations. So I bring a 12 pack or something, people can have if they want, but if there’s a few left I’m taking them, maybe leaving some for the host.
I’m not going to say it’s rude, but I wouldn’t say it’s proper.
If I’m hosting a party and you bring a 12 -pack, I’m going to assume you thought I would enjoy the beer either during or after the party. I would expect that you would drink a few of them, as well.
If you grabbed the remaining beers as you left I would think “What the hell?”. Leaving with them indicates you brought the beer solely for your own enjoyment.
The only time it’s ok is if its a large, open invite, BYOB event where the host provides only the space and you are expected to drink entirely from your own stash. I wouldn’t leave my good beer to be drunk by strangers at some massive anonymous house party.
If the host provides anything, even a bowl of chips or cans if PBR, leave it. It’s a host gift, and a little bonus for their gracious hospitality.
This is an interesting dynamic. You see, in my circle of friends, it’s a given that whatever beer you brought, was strictly for yourself.
It would be a totally different story if it was just me and my GF, you and your SO. We’re all having a quiet dinner together then I break out a bottle of Crown for us all to enjoy. Go ahead and keep the bottle my friend.
But then again, I don’t consider that a party. I wonder if some do and we’re just mincing over words here?
Leave the Keystone Light that you brought and take the host’s Westvleteren 12 with you. Duh, people.
Same here. It inevitably ends up with the host opening a bottle of Bulgarian brandy, or suchlike, that’s been at the back of a cupboard for ten years.
I would never consider taking beer home with me regardless of the size of the party or my relation to the host/other guests. I’m not going to say it’s definitely rude, but it might generate a raised eyebrow if I saw you waltzing out with the remnants of your 12-pack (particularly if the gathering isn’t over).