Recommender choice for admission to a MSc program I am planning to apply for an MSc program in Northern Europe or the UK, starting September 2014, which typically requires two recommendation letters from my former university professors. I have the following dilemma:

I have a personal relationship with two professors from my faculty, whom i know are going to give excellent recommendations for me. However, I chose neither of them as my supervisor for my Bachelor thesis, and I prefered to work on it under the supervision of a third professor, whom i have a slightly less personal relationship and spent limited time with during my undergraduate years (reason for that being my subject of choice overlapping with his/his groups research). In fact I only had extensive direct contact with one of his PhDs, under the guidance of whom i conducted my project.

So what I really want to ask is: Is it considered necessary for one of my LOR to be given from my thesis advisor? Is it going to look bad or somewhat odd to the eyes of the admissions committee if not?
If possible, it is always better if you can get a good letter of recommendation from someone who has actually supervised your research, because they can directly comment on your promise as a researcher. At the master's level, however, I don't know if it's quite so important as at the doctoral level, particularly because some fields may not require a bachelor's thesis (they may have a senior project, laboratory, or design course instead). 

In the present circumstances, this would be one of those times where you should check with the places you're applying and ask if you can submit a third letter of recommendation. Then you get the advantage of having two people who know you well personally, plus someone who can comment on your research.