Your best option is to use an Hex editor. Most Hex editors are developed to handle huge files. They can search for either strings or hex sequences.
Some hex editors can also dump the content of RAM, read entire RAW disks or dump them, it depends on the editor.
Have in mind that some RAM areas won't be accessible for obvious scuritysecurity reasons. So if you are trying to hack some password from RAM you probably won't get it. Life is not that easy.
This method is usually used to debug, not to hack.