First I would ask what you consider unambiguous in return. I can be, and usually am very unambiguous in what I say and write, except when I am writing poetry or stories. The only problem is that people will always interpret what they hear and read according to their own biases.
Lojban is a created language from the LogLan (short for Logical Language, the name of the group that created Lojban). There is another such language, Esperanto, though they do not claim to be unambiguous. The truth of the matter is that any language can be ambiguous due to lack of personal vocabulary, incorrect word and grammar use, and other things.
Lojban is an attempt to create a new language based of multiple languages with the intention of being unambiguous, but from what I have read already, many English speaking people won't be able to use it because they may never grasp the ZAhO tenses.
Most languages have an area of weakness. English is one of the best languages for science and technology, but it is also one of the most difficult languages to learn, let alone master; and it falls short in other areas. Spanish, both European and Latin American versions are better at expressing feelings.
So, in my view, there are no unambiguous languages at all. Though now you have interested me in Lojban. Might be fun to learn just for the sake of it, and maybe become one of those who helps it take off. Besides, more people using it would start the NSA having fits with having to program the language into their systems. LOL :D
Thanks for bringing this language to my attention. Perhaps, I shall know the answer in a few months of studying Lojban.