Finance

It depends on individual's interest and other factors like, your field of graduation and your career prospects.
Major disciplines in MBA, you can look for are as follows:
1. Operations: It needs analytical knowledge with fair hands on mathematics. You will get job profile like operations manager, supply-chain manager, resource manager, etc.
2. Finance: It needs basic knowledge of accounting and share, equity, credit-debit transactions. Related job profiles are in corporate treasury, business operations and credit analysis. Such jobs are typically offered by companies such as Goldman Sachs, JP Morgan, Nomura, RBS, Barclays, etc.
3. Marketing: It deals with the promotion and advertising strategy to convince the target customers for your product. Job profiles are in digital marketing, sales, market research, market analyst, etc.
4. HR: It requires good communication skills to deal with your team. You need to get the best out of your team and keep them motivated. Job profiles are like employee manager, labor manager, customer relation manager, etc.
5. Data analytics: With the digital revolution, making sense out of big data is becoming increasingly important for all kinds of businesses be it banking, retail, e-commerce or management. As a result many business schools have now started offering data analytics as an important part of their MBA programs. Companies like Fractal Analytics, LatentView Analytics hire MBA graduates as data scientists or data analysts.
As you will be complete your BBA, you can go for marketing, finance or HR.