The more complex kitchen islands that include a sink and sometimes also a stove with a fume hood.
These islands require more planning. When you already plan to renovate your kitchen and its floor, you might think of providing water, gas and electricity for the island. Once a complex island is done its less flexible, but the advantage is that you face your guests more often during preparing the food and can participate in the communication better. Also you might have more light and space during work then in a classic kitchenette facing the wall.
First, some of my island finds with sinks only: