The entry fee to a house party is pretty standard: a six-pack of beer or a bottle of wine (which explains why sometimes you end parties with five more bottles of mediocre Merlot than you started with).
But if you're looking to step up your party game, don't just grab whatever vaguely craft-looking beer is at the corner store. Grabbing a few bottles that together make a zero-effort yet foolproof cocktail will show off your booze cred and up the quality of drink at the party at the same time. No mixing, no shaking, just pour and go.
And if you really want to be a hero don't forget the cups and ice. Just about every party runs out at some point, and there's nothing sadder than watching someone sip warm gin out of a coffee mug.