I'm not suggesting that it is a good idea to build a hash that big, I'm just pleading guilty to having done it...
It was a Perl script to create a cross reference to an outrageous number of stored procediures doing all kinds of truly perverse things (cross database and sometimes even cross server access). The script took a long time to build, but it was tracking a truly horrific number of references to an unholy number of objects, so it was way better than trying to do it manually.
-PatP