There are a few that I had forgotten about, that are now going to be on my list of 'most used!.
For example, I will now use Command-Shift-D in Finder to quickly get to my desktop folder.
I already frequently use Command-Tab to activate the App Switcher and to switch between running apps (ie by continuing to hold down the 'Command' key as I hit the 'Tab' key.) Each time I hit Tab while holding down Command takes me to the next app on the right.
Reading this article, I have also discovered that I can use Command-` (which the key to the left of the number 1 key) to move between the apps from right to left while I am using the App Switcher.
So Command-tab to move from left to right, Command-` to move from right to left.
Much easier than having to cycle all they way through my apps to get back to one I have tabbed past!
Check out this article to see if there are other shortcuts that you may not yet have discovered!