I wonder if Hungarian is particularly good in this way. It's agglutinative, like German, so the words can be unbearably long, but the grammar of Hungarian is interesting, in that word order is much more flexible than other languages. Sentences can be said in multiple word orders and still be "correct", while the emphasis required by word order gives nuance and helps to shape the precise meaning of the sentence. The Wikipedia entry gives some examples. I'd think that having that kind of flexibility available in a native language would be a benefit... I've heard that the grand history of science and mathematics in Hungary is credited to the kind of mental flexibility that speaking Hungarian offers. In some sense, math's commutative and transitive properties are built-in to the language itself.
Full disclosure: my knowledge of Hungarian consists of a few common words and phrases, and lots of food words... I do love the food in Budapest.
There are also many constructed languages that are specifically designed to facilitate thinking, but, of course, they're not in wide use. Ithkuil and Loglan are well-known examples.