[wxHexEditor](http://www.wxhexeditor.org/) is (nearly) perfect for this.

 * Opens 10 GB+ files without any problem
 * Very fast text search: ~1 minute to search a pattern in a 10 GB file whereas it takes 21 hours with another tool I tried (LTFViewer)
 * Only drawback: I haven't found an option to display the text with newlines like a normal text. Only a hex view and a string preview right panel