Aside from the dollar sign ($
) and underscore (_
), I don't think there are any "basic" characters that aren't taken by basic operations or string delimiters.
Edit:
Basically, this means you'll have to give your short-hand a different name if you expect your code to be used in combination with jQuery / underscore.js
However, like Deestan mentioned in the comments, you can use (pretty much) any ASCII letter as variable name, as long as it isn't taken. Then, it's just a matter of convenience.
Accents like û
are relatively easy to type. The more elaborate characters could require their ASCII codes to be entered manually, which kind-of defeats the purpose of a shorthand alias.
For example, while impossible to type, this is valid js:
.
Ḣ̶̤̟͍ͦe̱̺̺̮̗̼̖ͫͭ͜͟ͅ ͚͖͙̻̈́̏ċ̨̟̖͙͈̲͇͙̬̲ͩͭ́́́o͎͓̘̭̱̩ͮ͂ͯ̿ͩͨ͂́̚̕m̬͎̜̪͋͛̏̇̊̆̋̉̒͞ę̝͕̯̯̗͋ͩ̿̈́͒̓̾͝s̸͔̜͇̔͊͢ = 'Some text';
.
(No syntax formatting on it since that breaks the effect)