This is getting dangerously close to a philosphical discussion, but if you keep things simple, you'll have fewer things to worry about, and are therefore less likely to make mistakes. Speaking personally, I would limit myself to variables starting with letters and containing only letters, underscores and numbers. It makes the code easier to read (in theory), and you will spend less time later being confused. Assuming, of course, you are as easily confused as I am.

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tbone1
Ain't enough 'O's in 'stoopid' to describe that guy.
- Dave "the King" Wilson