Full frame cameras really put a lens to work; if you don't want vignetting you will have to gets some very expensive glass.
Even the most expensive glass vignettes as well. Well...most of it. If you buy a fancy Zeiss prime then you might not get much vignetting wide open, but on any expensive zoom (and uber-bright f/1.2 primes) there seems to be a certain amount of vignetting that seems to be inevitable.
I typically don't mind it that much. Usually it's not noticeable enough to matter unless you're photographing a consistent color such as sky. I happen to like the vignetting of the Canon 50mm f/1.4 when its wide open.