Перевод - Испанский-Шведский - Soy una persona muy rara. Pero todo puede pasar.

To me "sällsynt" sounds good like special (the others: ovanlig, unusual, not normal maybe and annorlunda, different kind of person, eccentric maybe) Let's see what the swedish expert says...

But I don't know the meaning of 'rara' here.

Spanish "rara" = English "rare": a "rara avis" is a "rare bird", something unusual, exotic, exquisite.

One swedish expert came and edited the second sentence, but didn't do anything else. Accourding to Unas explanation, this is right, isn't it?
I thought it could have a very different meaning, as always happens to spanish-portugues words.