I suggest you use a tool such as long tail pro or Google keyword planner and analyse the top 10 ranking sites in Google for any keyword you find that has a monthly search estimate of less than 2,000 searches per month to find low competition keywords.

There are many popular niches, and they all have low competition keywords within them.

Only thing I concern is top 10. I don't care many competitor. When I begin, I go with difficult keyword.
When I try to do something, always try to do hardest thing.

All profitable niches are going to have competition. Don't let that frighten you. It just means there's money to be made. How to do proper research is something you learn. The niche you're in doesn't matter because the techniques you employ will be the same.

As far as the niche you should start out with, I recommend that you make a list of your hobbies and go from there. Almost everyone has at least one hobby that's part of a profitable niche market. Magazines and using sites like Amazon can help with this. They are basically broken up into niches. Choosing a niche whose products and people you're already familiar with will help out a lot.

Joey

Yeah, I agree with the above post.
Sometime profitable nick has a tough competition in the market and difficult to survive with them at the starting period. Start with the your idea and analysis and work for go ahead.