Opinions--best separator for use with loadVars

I have a project that needs to store user input on the server, then be able to reload it later.

I am interested in opinions as to which separator would be best to use, ie comma, semicolon, tilde, etc. Of course whichever character it is, it will be restricted from usage by the user, so it must be uncommon.

I’m leaning towards using the tilde, since I already use input textfield restrictions to prevent backticks for server security (same key on the keyboard). Seems to me as if the tilde is a very rarely used character, and so should be fine to exclude it from user inputs as well.

Anyone think a different character would be better, and if so why?