The most legitimate use for this is for top-level namespaces, which need to be short or they'll junk up your code like crazy. jQuery already took $, and Underscore took _. Maybe 木, ϗ, _⃗, 个, î, 人, Ǝ (not ∃, that's illegal!), ℵ, 二, ℜ, 龍, ℕ, 八, Δ, 大, ʃ, ː, 卐, or as mentioned below, λ? ˀ is probably too obnoxious though.<p>For no particularly good reason, ☺ and ☠ are illegal. I think the Plan9 strategy of considering non-ASCII characters as identifier characters by default is probably a better one than changing the language grammar every time the Unicode standard revs.<p>(As mentioned in another comment, <a href="http://canonical.org/~kragen/setting-up-keyboard.html" rel="nofollow">http://canonical.org/~kragen/setting-up-keyboard.html</a> <a href="https://github.com/kragen/xcompose" rel="nofollow">https://github.com/kragen/xcompose</a>. The Chinese I copied and pasted from <a href="http://www.mdbg.net/chindict/chindict.php?page=radicals" rel="nofollow">http://www.mdbg.net/chindict/chindict.php?page=radicals</a> though.)