Right next to my batarang and bat-zip-line-hook-shooter-gun on my utility belt is my SQL Server DBA Tool Kit, full of scripts I've picked up along the way.
I take little credit for some of these, as I've picked them up from various sources. I have modified them, for example, adding the ability to see the cached execution plan to MS PSS's "worst queries" query, or adding a blocking chain and cached execution plan to the typical dm_exec_sessions and dm_exec_requests queries out there to replace sp_who2.
There are some of my handwritten queries in there, for example the query to find the largest objects in the database and their compression state, a proof of sql_modules vs INFORMATION_SCHEMA.routines, and the "sessions and requests" with blocking chain query that I've presented on before and use daily. Nothing novel or ground-breaking, but real practical utility queries I use personally as a SQL Server consultant.
I presented my toolkit last night to the Baton Rouge SQL Server User Group and it turned out to be one of our best meetings in a while - over an hour of solid, experience-based conversation about queries, best practices, example experiences that was a wealth of information. Thanks to everyone who attended and helped make it a great meeting - it certainly wasn't all me and my fancy tool kit.
You can view my SQL toolbox on Github.
EDIT: 20140813 Updated toolbox link.
EDIT: 20140929 Updated toolbox link.
EDIT: 20170830 Updated toolbox link to include Github.