HxD does everything a hex editor should, and it has all the options a hex editor should have. With it, you can insert bytes, fill sections, and view files in DOS/Mac/IBM/ANSI/EBCDIC ASCII formats. There are the normal cut/paste/delete functions, plus more esoteric functions such as the ability to export to HTML, text, java, c source code, 16/20/32 bit Intel hex, and more. The program will open files of any size (even greater than 4GB), edit memory as well as information written to disk (as a stream, not sectors), and even edit disk images. It can generate checksums for any file in a number of formats as well as compare two files and analyze byte patterns.
Mr. H?rz doesn't waste time needlessly prettifying with bitmaps or straying from the Windows GUI norm. Every option and function is neatly labeled and placed where it makes the most sense--a model of design following function. The program is lightweight, very fast, and a must-have for anyone who requires the ability to edit non-text files or memory.
Caveat: Hex editors in general are for geeks only. You can cause a lot of damage to your disk and files/operating system using a hex editor without the requisite skills and knowledge.
--Jon L. Jacobi