While writing my previous topic (about ReSharper ALT+INS), on thing came to my mind: how about adding some intelligence to the "override method" dialog, where it would highlight or in some other way tell apart the most likely "overridable" methods?
I'm sure that we can argue for a few months about what defines a most likely overridable method, but empty methods are a good start. Annotations also pose a very attracting alternative, but there's no 'standard' annotation for such methods today. Puzzling enough, Sun defined an annotation for overriden methods, but couldn't fathom that their users would like an annotation to mark extension hooks.
P.S.: I know half of you will scream: "OMG! A properly designed class makes this useless, and only the extension hooks will be overridable!", but keep in mind that the other half of us work with legacy, improperly designed code :)