If you ever thought about pimping your bokeh in an experimental way, here is a nice and easy howto.
The shape of the bokeh is defined by the shape of the aperture. Usually a lens has eight or nine a bit curved aperture blades which model a more or less perfect circle resulting in the typically circle bokeh (see the fist picture). So if you use a wide aperture and add a smaller stencil in front of the lens the bokeh will have the shape of the stencil instead of the shape modeled by the aperture blades. In picture two I used a star stencil and in picture three a snowflake stencil resulting in little star and snowflake bokeh. As you can see in the three picture I used the handlebars of my bike as focus point.
Here is how I did it: