I was trying to figure out how to take my vodka, and came up with something pretty cool. You need the pickled shisho (beefsteak) leaf used to color umeboshi (salted plums) red. Take a couple leaves, and drop them into iced vodka. Bite off a little and chew them while you drink it. It's delicious.
I also tried doing stuff with the plum itself. The sugars in the plum brought out the bitterness in the liquor, so that part of the experiment failed.
The principle seems to be: aromatic and salty things go well with dry liquors like vodka and gin.
I think you *might* be able to get the leaf in some jars of umeboshi. I get mine from my mother, who makes the plums.