SmartBear's Code Collaborator takes all the chores associated with a code review and automates them. Packaging the code up for a review, providing feedback exactly on the line that you want to comment on, sending the feedback, responding to the feedback, arguing over a line or issue, and so on. Developers actually start to enjoy doing reviews. The defects that the reviews prevent are one of the most hairy ones. I had one of the best software engineers tell me that there was no way that the team would've found a given defect without the review, because it was obscured by other behaviors. But in the review they were staring at the code and the code didn't make sense, so they fixed it.
We also coined the term "reverse code review." This is when an experienced software engineer sends a review to multiple less experienced software engineers with the intent of sharing a solution or teaching a pattern. It works well to improve the strength of the team.
Two of my teams have used it so far, and both consider it a useful tool. The first team told me to figure out how to pay for it, because they don't want to give this tool up after the eval period was over... Disclaimer: I wrote a chapter for the Best Kept Secrets of Peer Code Review book. But that came only after we used the tool, and absolutely loved it.