For me another two way merge would be useless bloat, but the infrastructure for a good three way merge with sublime-style multiple select would be mindblowing.
The only program I've seen that does something like this is GNU emacs. There was a command for comparing the buffer with the corresponding file (diff-buffer-with-file).
$ cp ~/Library/Application\ Support/TextMate/Bundles/BUNDLENAME.tmbundle ~/Applications/Sublime2 ~/Library/Application\ Support/Sublime\ Text\ 2/Packages/
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