A few awesome KDE keyboard shortcuts, some I forgot, some I never knew and just said "wow, what a great idea".
Show Window List: Alt-F5
This is similar functionality to Alt-Tab (which is called "Walk through windows") but will always show windows from all desktops, even if "Walk through windows" is set up to only show windows from the current desktop.
Show the Klipper Menu: Ctrl-Alt-V
Klipper is a handy utility that shows up as a clipboard on the right side of your taskbar. It remembers things that were recently on your clipboard. I use Ctrl-C and Ctrl-V for copy & paste, so having a keyboard shortcut to pop up the Klipper menu just makes me that much more efficient. If you copy snippets from several places then paste them one after the other (for example) then this could ease that type of work.
Activate Window Demanding Attention: Ctrl-Alt-A
When some programs start (like the Gimp for instance) they open more than one window. For me, when I start the Gimp the toolbox window opens and another window for Layers, Undo history and Paths opens. One window gets the focus and the other one is minimized but flashes in the task bar. The flashing is a way for the window to demand attention. So Ctrl-Alt-A will quickly switch to that window to stop the blinking and let my taskbar hide away again.
I got these from a note I left myself months ago. If you need more then here's an extensive list from a while back