This question will be answered based on people's expertise, strength and interest. So, its very subjective. Basically, there is no such thing as a worst or best optional subject. All the subjects are worst and best at the same time. It depends on criteria you have taken into consideration for judging that subject. So, recognize your strength and interest and choose the subject that suits you the most. It is your choice. I bet you will the opt for the BEST Optional subject if you choose it by yourself rather than being influenced by opinions of some random people. But, here are a few things that you can use as criteria to choose your optional subject: 1) Syllabus Lengthiness - Few subject like Anthropology has very limited syllabus, just read the syllabus if you feel your interest can be inclined with this subject then go ahead.2) Availability of Materials - Point is self explanatory go with optional which has enough content to study from.3) Take Subject which can cover GS papers as well - For example you are working and don't have time to cover lengthy syllabus of gs and optional then better take Geography, IR etc which are there in GS papers as well, Keep in mind you should be interested in that subject genuinely.4) Eliminate the Subjects - This is something you can do from starting, list out all the optional subjects. Now note down which optional you can never imagine to read like if you are not from medical background then Medical Sciences will obviously be not your choice etc. Short list 5-6 subjects which are of your interests then further analyse them with above points.5) Analyse recent trend, old question papers, scores of people, read interview of toppers who have taken those subject - All these effort will help you to think whether you can score well in the subject or not.6) As per recent trend few people take Literature subjects like Gujarati, Kannada literature and even people are preferring Hindi as their Literature subject since these subjects have very less competition considering you should have to cover in-depth knowledge of the subject then there are more chances to score well.7) Read for few days and then change again - If you in starting stage of your preparation then you can always taste the subject, old question papers and few starting introductory videos and decide whether you are not at all comfortable with those subjects, Read interview of few toppers who have changed their subject after their 1st or 2nd attempt so don't hesitate to change the optional if you are not comfortable with it. Hope this will help you!