These recommendations always get trumped by personal knowledge so if you know someone likes a particular kind of booze then definitely go that route instead.
You aren't the only person invited, nor the only one bringing drinks so why play it safe? If it's a dinner situation then branch out with your wine and get a boutique varietal like Warrabilla's Paola's Reserve Zinfandel. Most people don't know much about Zin's and this one is one of the richest tasting red wines you'll get under $40. Pure class.
Dinner With the In-Laws
Do NOT try to impress. If you pull out a fancy bottle then you're fiscally irresponsible, if you pull out a cheap bottle of plonk you're not good enough for their little girl. Play a straight bat with a $30 shiraz or cabernet sauvignon from Barossa, McLaren or Coonawarra that's got a few years on it.
A Gallon of Margaritas... Not even joking, people always play the birthday far too safe, you're allowed to have fun! Jeffrey Morganthaler has the best bulk margarita recipe or you can buy MX bottled Margarita the only premium pre-made margarita; just pour, shake/blend and serve.
Beer. Not just any beer but beer that no-one has heard of and everyone will like, even people that hate beer. I'm talking Berliner Weisse, it's a light sour style that is far more like a vodka lime and soda with the finesse of champagne and it slaughters summer seafood and salads. Top pick is Boatrocker's Orange Sherbet Berliner Weisse.
Stay classy early on and introduce everyone to an interesting scotch before things start getting rowdy. Benromach Hermitage wood finish or their 100 Proof 10 year old if you want a bit of smoke and heat.