Hungarian

Meet the only 'independent' language on this list. This means that no one really knows its origins and hence, they aren't linked to any base language either. This makes Hungarian both utterly unique and highly complicated learning material to say the least. For one thing, it has about 7 different verb conjugations while each and every word is also broken down into male, female and neutral genders. 

Then, it has 35 cases or noun forms which is more than any other language on the planet besides being choc-a-bloc full with highly expressive and idiomatic words and suffixes. The high recurrence of vowels and the deep-throat sound it makes when spoken makes it one of the hardest to speak as well. At the end of the day, many have complained that even after learning it, it's close to impossible to maintain what you've learned without daily practise!

-Picture courtesy thinkstock-