Line and Polygon will use all points given to them to create a shape.
Rectangle will use the first two points as top left and bottom right corners.
Circle will use the first point as center, and requires the radius: option to display. Note: To view circle from initial zoom, set options to radius:1000000.
All possible options can be found at the google maps API documentation.
A few good examples for possible options are:
editable:true or editable:false will choose to lock the shape as is, or leave it open to change.
fillColor:'color' and strokeColor:'color', will recolor the shape or border for any CSS3 compatible colour.
fillOpacity and strokeOpacity each take a double between 0.0 and 1.0, and determine how solid to make the shape appear.

Relevant sections of the Google Maps API: Polyline, Polygon, Rectangle, Circle