Bringing a rare or specialty beer brand to a party tells your host/hostess, "I care enough to go somewhere other than spätkauf!" (literally, "late buy," which is basically the corner bodega). Ambrosetti… has more than 600 brands from around the world on offer. Though this busy shop in Charlottenburg is practically a Berlin institution, its beers are super cheap -- generally around €0.70 a pop. [link]