I'll wholeheartedly agree with a stock Aston Martin V8 Vantage as being quite testy... a lot of fat + a lot of grunt = one senseless pig. You usually get a feeling that the nose is wandering wherever it pleases (if you can figure out where it is, since it's so big), and there's not enough weight on the rear wheels to keep them from lighting up at inappropriate moments.
While I would've agreed with the Speed 12 if asked less than a year ago, I've driven it enough that I really like it, even if it does need more traction. The Zonda is another car that less than a year ago, I would've considered it sloppy, but now I think its handling is pretty close to brilliant.
I'll also agree that relative to the R390 and 787B, the Toyota GT-One is quite a handful. My issue with it is that it seems a bit "floaty", as if the tires aren't always in contact with the asphalt.
The Mercedes CL600 can also be a bit of a nuisance to chug around, since it also suffers from a wandering nose and no rear traction.