IMO the two most secure browsers are Chrome, and Firefox with NoScript.
Chrome is a better default option because its secure sandbox applies to all sites, and doesn't get in your way. There are some reasons not to use Chrome, but it's not a direct threat to your privacy. If privacy against Google is a concern, you can still change the search engine, enable Do-Not-Track, and avoid using the "Sign in to Chrome" feature.
Third place goes to the latest version of IE, which has some sandboxing. There are certainly other reasons to dislike it ;).
Safari on Windows I don't trust at all really. (Native Safari may benefit from some sandboxing nowadays though). Opera gets marked down for not having NoScript (at least, nothing as well-developed as the FF version).
Firefox with NoScript set to "allow scripts globally" still protects against a few attacks (including the local router CSRF), and gives you the option of switching to whitelist-only if there's an unpatched exploit going around. Firefox is decent at blocking known-vulnerable versions of Java. And you can still block Flash globally (or install a FlashBlock extension, or enable the new builtin click-to-play). If you're not willing or able to use the latest version of IE or Chrome, it's a pretty good alternative; it just can't make up for the lack of sandboxing.