Automatic Vector Legends 

Automatic legends for vector plots include the style and shape for the vectors.

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X Grid[Partition[ VectorPlot[{{y, -x}, {x, y}}, {x, -3, 3}, {y, -3, 3}, PlotLegends -> Placed[Automatic, Below], VectorStyle -> #] & /@ {"ArrowArrow", "BarDot", "CircleArrow", "Dart", "DotArrow", "DotDot", "Drop", "PinDart", "Pointer"}, 3]]

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X

Automatic legends for stream and vector density plots include a color bar for the field magnitude.

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X VectorDensityPlot[{y, -x}, {x, -3, 3}, {y, -3, 3}, PlotLegends -> Automatic, ColorFunction -> Automatic]

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