That reminds me of going to a dinner party a few years ago, attended by 4 other dinner guests.  One guest did, in fact, bring a bottle of previously-opened wine.  Its contents had been  partially consumed by 1/4 or 1/3 prior to arriving at our hosts' residence (we met in the elevator).   No, this guest did not drink the wine during the elevator ride--I think he just brought the bottle that way from home.

In addition to bringing wine, I usually prepare a tin/package/box of home baking (savoury or sweet) that our hosts can enjoy at another time.  I label this item re contents and storage--and make a point of telling our hosts it is a gift for them to enjoy when they choose.