The tools I use

Snorkie could have drowned

As a DBA who is currently involved in some HA/DR aspects of the job, a lot of the core DBA work (backups, monitoring, users), and is also a performance tuner/developer -- and is the lone DBA -- I need access to tools to help me get this job done.  Below is what I am currently sporting in no particular order.

Core Work(Monitoring, Backups, Troubleshooting):
We currently use Idera SQL Diagnostic Manager for alerts on blocking and long running queries.  We also have Nagios and Zabbix running which tell us things from and OS/File perspective.  If I am on a server I am using sp_whoistactive to get whats going on in the instance.  If I need to drill into an actual spid to do a trace, I use the SQL Server Profiler.  Backups are handled by Ola Hallengren's lovely scripts, as are Index and Statistics maintenance.

For Development:
I am currently using ERStudio for design and are pushing everything up to a team project server for version control.  That is, unless I just decide it's less frustrating to use my hands.

For Tuning:
I personally use the sp_Blitz scripts quite a bit.  These provide a lot of information, and save a lot of running around putting together queries on the DMV's.  To get those table statistics, or whats going on in the cache, this is a good go to.  Past that there are some other useful one off queries I have accrued in my travels.  As for explain plans, SQL Sentry Plan Explorer Pro just went free so that's something I have added to my repertoire recently.  And of course -- set statistics io, time on...