short answer - all of them. And I think I have enough experience to say that ALTHOUGH.... one breed I've never owned is a Pit Bull.... and they have the worst reputation, by far.

Every breed I've known has had 'good' examples and 'bad'.... I think some are more likely to lean 'good' than others... but like RamUK says, owners very much come into play.

I've known VERY few, and I mean VERY few, bad tempered Labs. I don't think I've ever known a 'good' tempered Chihuahua.

German Shepherds are scary... NOT because they are bad tempered, at all... but rather, they are smarter than humans and KNOW it. When you go to train a German Shepherd all of them will quite revealingly let you know that you're going about it all wrong.

Doberman's... agreed with other's here... unwarranted 'bad' reputation. BUT... you can't stare down a Doberman... don't even try.