Identify slow query without slow query logs in mysql server
If you do not want to enable the slow query log at all, I have a suggestion
You can use pt-query-digest over an interval of time.
I have suggested this a few times in the DBA StackExchange

Nov 24, 2011 : MySQL general query log performance effects
Apr 24, 2012 : Investigate peak in MySQL throughput
Jul 26, 2012 : What is running right now?

If you look at my Nov 24, 2011 link, I provided a shell script you can crontab to launch pt-query-digest.
GIVE IT A TRY !!!