Use only 2D pie charts, and label each slice with its corresponding percentage.
A rant about 3D pie charts
Never use 3D pie charts. They misrepresent data.
The important parameter of a pie chart is area. If the pie is represented in 3D, the foreshortening skews the area of each slice and the chart becomes misleading.
In the example below, the 1% slice is at the "back" of the chart – the perspective imposed makes that slice look smaller. Bringing this slice to the front would similarly skew the look of the chart, making the 1% slice look bigger.
Note how much larger the blue and green slices appear in the chart below, now we have restored the visualization to its correct 2D configuration.
Think about data vizualisation: graphs are not there just to look pretty; they must accurately convey the data.