Yes, you can do an infinity bottle for any hard spirit. Whisk(e)y, rum, and cognac are the more popular variants. Vodka/tequila less so.
You can "do" pretty much anything with your half gone liquor bottles (you could even dump 5oz of Gueuze into 20oz of liquor and it would probably protect it) but like holldy01 said, most civilized people try to have a theme to the bottle lest they just turn into "jungle juice" (or a really peated mess). If you have a Glencairn with 2oz of bourbon and add literally drops of peated whisky, it starts to takeover quickly.Recently went to a Glenfiddich tasting w/ the east coast rep and infinity bottles came up. She has at least 4 going right now-bourbon, rye, Islay and a highlands/speyside