FlavourArts "Irish Cream" tastes amazing all by itself. It reminds me of hot cocoa mixed with Baileys irish cream. Their Tutti Frutti and Torrone taste fine alone too.
Vapor Renu's "Banana Nut Bread", "Creme de Menthe" and "Big Red Gum" also taste excellent alone. Perfumer's Apprentice "Cola" and "Plum" and "Toasted Marshmallow" also taste great.