Atlassian Crucible - Collaborative peer code review tool.
Refactor.io - Share your code instantly for refactoring and code review
Review Assistant - Review Assistant is a code review plugin for Visual Studio.
codebeat - Automated code review for Swift
MergeBoard - MergeBoard is the first code review tool to display code changes in a smart way. Its unique features help developers spend less time on code reviews and catch more bugs.
Stickler CI - Focus on your project, not formatting.