Do note that is actually supposed to be Cmd + ` (the same button as the ~, and not single quotation mark)
Thanks X-Istence, was typing on my mobile with swype, got the wrong character. Corrected in the original.
Except in Office 2008, where Cmd-‘ is broken! If they didn't fix that in 2011, I am going to switch to OO.o out of spite.
Hmmm, this combination works correctly in Office 2008 on my MacBook Pro (used almost daily in Excel and Word) in Office 2008 [ver. 12.2.3 (091001) on OS X 10.6.4].