[jdnier]

Works in Firefox, not in Chrome (at least on MacOS).

[yorwba]

What about

  data:text/html,<script>alert(2+2)</script>

?

[ConfucianNardin]

Works in both Chrome and Firefox.

[tomc1985]

Doesn't work in Chrome (edit: or Firefox for that matter) for Windows either... that's a shame. Abusing javascript: is a really useful trick for lots of little hacks.

[striking]

It's also an attack vector for hacks. You can enable it on some browsers if you please, but having it off by default is sensible...

[johnhenry]

Works if you type it out. If you paste it, the "javascript:" part will be omitted.

[abhinickz]

Above works even if you paste it.