I use Pixie[1], which works really well even on Windows 7 and 10. It's an 11kB portable app.
There are a couple of other cool tools on the page too that I weren't aware of, like this:
http://www.nattyware.com/fontster.php
It's a HTML + Javascript desktop application that weighs 2 K. And it even uses native widgets and looks and feels like a real application. Isn't that something... ;)