I've been told that Lego is obviously geeky and sometimes I like to play at geek. So consider the following, you buy some Lego at a yard sale and you come across a piece which looks like this a lego piece, round at one end with a long flat tail at the other. My first thought was that that was a rather silly and specialized piece. Then I realized that clearly it was specially created to make a horseshoe crab (limulus): lego horseshoe crab viewed from above.

Here is a view from below and an expanded view in case you would like to make one: the lego horseshoe crab viewed from below, the pieces all layed out. The grey pieces are the rarer shade of dark grey. This is simply because it is what colour that original special piece happened to be. The brown and black pieces were used because I didn't have the right pieces in dark grey; this also explains why one of the pieces has some stuff printed on it, barnacles we'll say. Also as pictured there are no hidden structural pieces, though you could profitably put some under the rightmost piece on the top. As is typical the small images above are links to larger ones.