Aniseed is probably one of the more unique flavours in an E-Liquid and it can certainly divide vapers into a love/hate experience.  Aniseed originates from the flower and is used in many different food and beverage uses around the world.  The flavour is sweet but carries a very distinct taste and can amplify or ruin an E-liquid.

Aniseed flavoured concentrates are often used to give either a distinctive underbody in an E-liquid or to give a flavour a kick in an otherwise light flavour.  Aniseed flavoured E-Liquids are often strong and overpowering if used in large amount so less is more when it comes to using aniseed.
Aniseed has a tendency to sit heavy on your coils in large amounts so it is advisable to use it sparingly.  However using a touch of aniseed in your Aniseed flavoured E-Juice can really bring it to life with higher watts really making the aniseed come alive.  Lower watts will benefit from a small amount if you enjoy an aniseed flavoured E-liquid.