There have been several N combinators, but none of them was quite as nifty as the more famous combinators (Y, U, S, K, and I are the ones that immediately come to my mind).

Yep, we know :). It's a "working title" (tongue in cheek)

Did you forget about the ninja combinator?!

I liked the bird hierarchy of combinators, myself.

In case you're wondering, I believe the reference is to this page:

http://dkeenan.com/Lambda/index.htm