Create a List-Tap, each time you call the component it will drop next item of the list (Use either F5 key(in Windows) or Ctrl+R (in MacOs), Grasshopper Timer to refresh the component or double-clicking on component )
You can Right click on "Drop Mode"(M) and choose desired Mode among four possible options

Inputs

Name	ID	Description	Type
Data List	L	List to get tapped	Generic Data
Reset	R	Reset	Boolean
Drop	D	Drop trigger (set it true in order to run this component	Boolean
Drop Mode	M	Define how to drop the items 0:Loop 1:Ping-Pong 2:Deadened 3:Repeat last (Optional)	Integer

Outputs

Name	ID	Description	Type
Drop	D	The current drop of the list	Generic Data