1. A plum brandy from The Balkans, similar to the Italian drink grappa.
Also spelled sliwowicz, slivovicz, sliwowitz, or šljivovica, and pronounced SLIHV-uh-vihts, SLIHV-uh-wits, SCHLIHV-uh-vitz, or schlyee-voh-vitz-ah (thanks to shallot for the last spelling and pronunciation). Real slivovitz contains between 50 and 70% alcohol and can make even hardened drinkers cough and splutter. It will also burst into flames if you wave a lit match over the glass. Good slivovitz should be served in a snifter like any other fine brandy, while low-grade slivovitz should be swilled like any other cheap intoxicant.
Update: (thanks to CapnTrippy for reminding me) This stuff is made elsewhere in Eastern Europe, including the Czech Republic, Poland, and, I think, the Ukraine.
2. A cocktail.
Shake all ingredients except club soda with ice, pour into a highball glass and fill with soda. Garnish with a slice of plum.
Obligatory Everything Bartender link.