Just a Classic.
With the exception of ABC (Fermat was probably built chasing Shadow and Tron :P) I think most authors on here have chased Fermat at one point or another, even now in the buggy, unsupported, much later version, it remains one of the best bots and a common WhiteWhale
. Though I don't think any amount of praise can put it better than Albert's comment at the top of this page. -- Kuuran