Write a hex editor
kinda boring, and there are lots of hex editors already out there.
Away.
it wouldn't be too bad. this one offers a lot of freedom in designing a elegant interface, handling large files, byte fills, etc...
there are laso a lot fo alarm clcoks for your cpu out there. but we had a contest on that be4. the idea is to come up wiht somethign challenging like this for programmers. not a new program dingy for the users.