Damond Walker started a pretty good thread in comp.lang.lisp with his post on how he first started using lisp:

  By sunday night I had the game done.  It was around 2000 lines of Lisp
  code, another 300-400 lines of C, and a 5 page paper which described
  the algorithms I used.

  I gave my presentation Monday morning and, honest to god, mouths hit
  the floor.  I had a few fellow students actually get mad at me.  My
  ego was pretty inflated at the time.  I think the prof still uses the
  game as an example here and there.  

Read the thread, but skip the... well, you know what parts to skip.