I know why he likes them its the sound of constant clicking and recently there has been commercials and movie's and TV shows with people doing just that. I used to at school it would annoy teachers just as much as they in turn would do it during test time.
These three are Acrylic.
The first is a Cameo/Orange with Chrome.
Triviet Chrome and Acrylic
both of which have depth of field which highlights the colours as can be seen below.