After 20+ years of application development, and systems administration. I have come you really like a few tools. (This list is NOT influenced by the fact I work for Teamstudio)
Here are my favorites in no particular order
Teamstudio, CIAO, Analyzer, Delta, Design Manger, and Snapper cool development tools.
Notespeek A window into the internals of you notes applications
Antrid change or reset the repid on a note application
MWsnap freeware screen capture tool
Deskpins A cool freeware tool that I first heard about from Andrew Pollack that allows you to keep a window on top of all others. Great for copy and paste type tasks
MS Visio I use this for creating notes Network Diagrams using my custom Visio stencils
Notrix The coolest data integrator for notes. My main reason is that you can use the windows scheduler to schedule jobs, and not have to rely on Domino to do it,
Dropbox synchronizing files between computers as well as hosting the files for this blog.
There are many more that come to mind but these I use or rely on the most.
What do you use and/or like?