Sambuca

I had never thought of Sambuca as a liqueur, but is considered to be one.

From Wikipedia:
Sambuca is an Italian anise-flavoured, usually colourless, liqueur. Its most common variety is often referred to as white sambuca to differentiate it from other varieties that are deep blue in colour (black sambuca) or bright red (red sambuca).

Sambuca is flavoured with essential oils obtained from star anise, or less commonly, green anise.... It is bottled at a minimum of 38% alcohol by volume. The oils are added to pure alcohol, a concentrated solution of sugar, and other flavouring.

The Oxford English Dictionary states that the term comes from the Latin word sambucus, meaning "elderberry".

Sambuca may be served neat. It may also be served on the rocks or with water, resulting in the ouzo effect from the anethole in the anise. 

Clear Sambuca becomes cloudy when water is added.

Like other anise liqueurs, it may be consumed after coffee as a ammazzacaffè or added directly to coffee in place of sugar to produce a caffè corretto.

A serving of sambuca can be a shot with seven coffee beans, representing the seven hills of Rome. Likewise, a shot with one coffee bean, called con la mosca, which means "with the fly", is as common. The traditional serving is with three coffee beans, each representing health, happiness and prosperity. The shot may be ignited to toast the coffee beans with the flame extinguished immediately before drinking.