Some (though not all!) things that you used to need to specify -webkit to use no longer require that for the versions of webkit browsers we support.

This brings back a ton of hits, though mostly in libraries and themes:

git grep "-webkit-" – *.css

A more focused place to start is the core styles of modules e.g.:

git grep "-webkit-" – */styles.css

We should first ensure that any usage of -webkit also has an unprefixed version.

Then we should remove any prefixed version that is no longer required.

Specific ones to consider for removal:

border-radius
http://caniuse.com/#search=border-radius
Not needed since Firefox 3.6, Chrome 4, Safari 4, Android 2.1, iOS 3.2

box-shadow
http://caniuse.com/#search=box shadow
Not needed since Firefox 3.6, Chrome 9, Safari 5, Android 3, iOS 4.3

(Similar applies to moz, but there's far fewer of those and the ones that exist (except for one in admin/tool/health/styles.css) are right next to webkit ones and so should get picked up anyway, and ms, o which I can't find any of)