I like Ack more than grep, but I agree: whitelisting file types isn't fun. I wrote a mostly drop-in replacement for Ack in C (https://github.com/ggreer/the_silver_searcher) and the biggest difference in behavior is the file filtering. Ag searches all text files by default, with the exception of those in .gitignore and .hgignore. You can also add patterns to .agignore files if you want finer-grained control. Oh, and Ag is much faster than Ack.

Ack isn't the only thing better than grep. If you're searching in Git repos, you might want to check out git-grep. Another useful tool is Exuberant Ctags: http://ctags.sourceforge.net/