I went on a shrub spree a few years ago, and while my guests loved them in cocktails, I usually drank them in sparkling water or seltzer or even just chilled water because I sometimes have an allergic reaction to alcohol, and they were just lovely without.
I recommend the cold shrub method - Michael Dietsch has a good book on it, some of his recipes are available on the Internet to start.
My favorites were lemon (like a lemonade concentrate but more intense), orange (like a better orangina or aranciata), and blackberry (intense and almost savory). Then you can mix and match fruit and herbs and flavorings. Ginger is pretty fantastic in fall and winter.