With one exception, my tools are all out-of-the-box.  I'm unsure how suitable they are for reluctant DBAs, but since you asked here are my staples

Windows PerfMon

SQL Trace

ClearTrace

DMVs:

 Expensive Queries:

   sys.dm_exec_query_stats as qstat

   CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) as qplan

   CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) as qtext

 Wait Stats:

   sys.dm_os_wait_stats

 Virtual File Stats:

   sys.dm_io_virtual_file_stats

 Plan Cache:

   sys.dm_exec_cached_plans as c

       CROSS APPLY sys.dm_exec_sql_text(plan_handle)

 Real-Time Blocking:

   sys.dm_tran_locks as locks

     JOIN sys.dm_os_waiting_tasks as waiters

PingBack from http://www.pythian.com/blogs/1115/log-buffer-105-a-carnival-of-the-vanities-for-dbas

in addition to the scripts posted above ....

- IMO the once in a while DBA needs SSMS including PerformanceDashboard !

- tons of ice to keep the head cool at incident time.

- a shortcut to a good sqlserver related forum.

- the guts to ask for more SQL-training. (Is this a pingback nowadays  ? ;) )

- A boss that is aware of the gamble he is taking and is willing to take the blames for this. (and not just rounding up the issue by firing his firefighter)

- and off course - I wouldn't be me if I didn't refer to it - a good fridge, to keep his beer at the desired temperature till the crisis is over :))