The following images show some of the many widgets currently found in VTK.
3D Slider widget
2D Slider widget
Box widget
Line widget
Implicit plane widget
Plane widget
Image plane widget
Point (or handle) widget
Sphere widget
Scalar bar widget
Spline widget
Checkerboard widget
Rectilinear wipe widget
Text widget
Camera widget
Playback widget
Distance widget
Angle widget
BiDimensional widget
Affine widget
Contour widget
Contour widget on Terrain
Logo widget
Seed widget
Caption widget
Balloon widget
Tensor probe widget