My Privacy Is No Longer A Chore Rated 4 out of 5 stars
Forget the hassle of "Private Browsing Mode" hiding your non-private tabs when you turn it on. Most of the time, HistoryBlock is even better than Chrome's Incognito Window.
All it takes is just take a few minutes, once, to play around with your AwesomeBar, find all the sites that might leave incriminating traces, and then you can sit back and browse without worrying about whether you remembered to switch to Private.
HistoryBlock is "always use private browsing mode" on a per-site basis, in effect if not in implementation. It's not perfect yet (It won't prevent dirty search keywords from showing up in the form field memory and it won't tell Flash that you're in private mode) but it's very close.