kdiff3 - KDiff3 is a file and directory diff and merge tool which compares and merges two or three text...
Kompare - Kompare is a GUI front-end program that enables differences between source files to be viewed and merged.
Devart Code Compare - Code Compare is an advanced file and folder comparison tool. Its intuitive interface allows you to merge differing files and folders fast and easily! And it's FREE!
IntelliJ IDEA - Capable and Ergonomic IDE for JVM
Beyond Compare - Beyond Compare allows you to compare files and folders.
Diff Doc - Compare files with 'Diff Doc' by Softinterface. Compare DOC DOCX PDF TXT RTF HTM XLS PPT. Command line capable for automating comparison of files.