For example in a line chart with dates on the x-axis and a KPI like sales on the y-axis it would be cool to attach critical events to certain values of the dimension.
Like for the date 1.3.2019 there should be an icon in the graph that when mouse-over pops-up up with the information that at this date we launched a marketing campaign.
I frequently get questions for jumps or if its possible to mark certain events.