/taskbarhide
Spybot - Search & Destroy
This parameter was added somewhere around version 1.0 of Spybot - Search & Destroy (SpybotSD.exe) to tell the application to run completely hidden, in contrast to the previously used background option /minimized that would still show an icon in the taskbar (hence the name).
Updater
SDUpdate.exe does support this parameter as well, in the same function as with the main application.