Five-spice powder is a powerfully scented mixture in which star anise and cinnamon dominate. It will also include spices such as fennel, cloves, nutmeg, Sichuan pepper and ginger (the name five-spice is symbolic rather than literal). Keep it on hand for making Vietnamese as well as Chinese dishes.
Five-spice powder is available from Chinese grocers, and is becoming more widely available in supermarkets too. A good blend should be fragrant and spicy but also slightly sweet.