Vodka is practically tasteless, which means that distilleries can add whatever bizarre flavors they want to it. For example…

Grass

Polish company Bak makes Bison Grass vodka. It’s not bison-flavored—it’s grass-flavored (and bison eat grass). The grass infusion leaves a small amount of coumarin, which is a main ingredient in rat poison and leads to liver damage (but then, so does vodka).

Horseradish

Sputnik, a Russian distillery, makes a vodka flavored with “pure organic horseradish.” Wasabi, another kind of horseradish, gives Green Geisha from Oregon’s Hard Times Distillery its distinctive flavor (and burn).

Pork

Bakon vodka is infused with the flavor of pork fat. The bottle is bacon-shaped, too.
https://www.youtube.com/watch?v=oaIOp9cp-oY

Pickle 

Another Russian distillery, Vodka Garant, makes a pickle-and-garlic vodka. If that’s not to your taste, American distillery Naked Jay makes a pickle-flavored vodka. No garlic.

Dessert

Pinnacle manufactures a line of dessert-inspired vodkas, including cotton candy, cupcake, cake batter, and whipped cream.

Peanut Butter

Van Gogh produces a PB&J vodka, while NutLiquor makes one free of jelly, just peanut butter. Both are, surprisingly, free of peanut products.

Bubble Gum

A company called Three Olives makes this vodka.

Syrup

Birch syrup is a sweetened tree sap, similar to maple syrup and widely used in Alaska. Alaska Distillery makes a birch syrup vodka. (They also make rhubarb vodka and their most challenging flavor: smoked salmon vodka.)

Arancnid

Skorppio-brand vodka doesn’t have any particular extra flavor, but it does come with a real, de-poisoned scorpion, much like a worm comes in a bottle of mescal.