Unable to install Wireshark on OS X Mavericks

Which version of Wireshark?

1.11.0 doesn't work on Mavericks, due to a problem with Qt.

1.10.2 does work (I just tried it), but the initial installation process is a bit of a pain:

• the installer package isn't signed, so you have to open it with control-click and say "yes, it's from an unknown developer, but I still want to open it";
• when you try to open it, it'll ask you where X11 is, and you need to click "Browse..." and browse to /Applications/Utilities/XQuartz (which you have to have installed);
• you may have to click the Wireshark icon a couple of times before it'll launch X11, and, even after that, you may have to quit the Wireshark app in the dock and restart it before it'll run the actual Wireshark binary.

After that, it should Just Work.