Definitely Swabians! According to my Berlin friends they have a reputation for financial accumen similar to the Scots over here (i.e. tight). Also, they have a dialect which is difficult for other Germans to understand (Schwabisch).
That said I have stayed in the Swabisch area quite a few times and found them quite charming hosts.
This reminds me about a British documentation about the Somme, where a Swabian officer was reporting the enemys progress to the German GHQ. It was interesting to hear a rather distinctive German accent in a British documentation, which makes it even more authentical to me.
Oh, and even the Swabians say about themselves "Being economical is not the same thing as being stingy." :wink:
Well, when it comes to stereotypes, most of them were already mentioned.