You mean it’s not part of the OS?

Variations on a theme...

I'm fascinated by the responses to
"How do you use your Dock?" and
"The multi-tasking Mac is always running" so I
thought I'd toss out another survey to further examine Mac OS X user behavior . There are certain applications (for lack of a better word) that I have been using for so long and/or that have become so indispensable to me that I often forget they are not actually part of the operating system.

Here are a few:

LaunchBar – I am completely helpless without this app.
StickyBrain – Universal note manager. What Apple's stickies should have been. My digital junk drawer.
HyperSpell – Instant access to Mac OS X's built-in spellchecker from any application (Even from Carbon applications)
WinSwitch – Fast User switching without wasting valuable menubar space
FruitMenu – I broke my Apple menu habit ages ago, but the contextual menu options are a must-have.
WindowShade – No genies or scale effects for me. I like double-click window shade simplicity.
PDFViewCM – A contextual menu for viewing PDFs in the finder. Why open Acrobat or Preview if you don't have to?
QuickImageCM – Fast and easy full-size image viewing and manipulation in the finder without launching any other apps.
QuickPlayCM – Fast and easy full-size video viewing in the finder without launching any other app.
CopyPaste-X – Your clipboard on steroids. I've used this for years now and actually put off my switch to OS X back in the day until this app was updated because I couldn't imagine life without it. The new y-Type addition may also give TypieIt4me a run for its money.
TypeIt4Me – Auto-completion and elimination of repetitive keystrokes. A huge time saver.
iClock – Menubar clock and calendar with an enormous amount of flexibility and numerous customisation options.
PDF Browser Plugin – Because PDF links on a web page should be viewable in your browser! Swift and simple.
Word Browser Plugin – Because links to Word docs on a web page shouldn't require you to open MS Word! Fast and free.
SnapzPro – Screenshots the way you want them. And movie recording too!
DefaultFolder – Open and save dialog enhancer. Save your files where you want them without wasting time drilling down through your folder trees.
AutoPairs – Auto-closing of tags, such as parentheses,
brackets, and braces. I can't remember what typing was like before I started using this utility.
Mount – Faster disk image mounting – even in Panther.

There are probably at least a handful of apps I am leaving out because I am so used to them... they have become such an essential part of my life that I simply can't think of what they are.

What tools have become an essential part your OS X experience?