Not an airsoft penguin, although that would be cool.
I'm making an airsoft pen gun, from a BIC pen.
I think anyone can do anything with pens, so I decided to do an airsoft gun. 6mm BBs fit perfectly into the pen body, and a couple of springs fit around the ink tube could provide a nice guideline for them.
I'm telling you, pens will thik for you one day. They will store data, write essays, and even paint classical peices of art, no kidding.