HxD is a carefully designed and fast hex editor including raw disk editing, modifying foreign RAM and handling files of any size. Its clear interface offers searching/replacing, exporting, checksums/digests, insertion of byte patterns, a file shredder, concatenation or splitting of files, statistics and more.
Editing works like in a text editor with functions streamlined to hide differences that are purely technical. For example you can view a drive just as one stream, can open it under Windows 9x or Windows NT+, undo, search, save, export or whatever you could do with a file. There is no sector-limited editing that gets in your way. The same holds true for the file size (also > 4 GB), which doesn’t affect editing speed and still supports undo. Or have a look at the RAM-editor that supports data-folding on every memory section and hides by default inaccessible memory, for a better overview but keeps the real offsets.