Sgrep (sorted grep) is a much faster alternative to traditional Unix grep when searching large files, because sgrep searches sorted input files using a fast binary search to find matching lines.
binreplace is a command line tool to search and replace binary sequences in a file. It can be very powerful when used together with grep and sed. It uses prefix tree internally to search. It's efficient even with millions of search terms.
Finddupe is a VERY FAST command line C program to catalog very large archives, identifying duplicate files even when offline. It has many features. You can easily grep a catalog to find what you have, and locate where it is.