I am curious as to what others find to be the most useful log analysis tools for *nix. Presently I am simply tailing output and grepping through things, however I'd like to use something that would be more feature full. In this case I'm watching Unicorn web server logs along with application output from staging and production servers that are collected on the local rsyslog server into separate files.
I have poured through the various log matches in the repos and the list is obviously quite lengthy and extensive, therefore I'm hoping that you might share the gem's that you've worked with or are aware of that merit special attention.