Well there is no one best startup idea but there are many interesting and fresh ideas. While it also depends on your test but some of the ideas that I found best to initiate a startup in are:-
1. Online journalism
2. Blogging for the e Sports Industry
3. Podcasting
4. Online assistant
5. Startup which supports the gardening industry
6. Online coaches
7. Yoga Instructor
8. Content marketing
9. Home-based startup
and a last one from my side would be Youtube.
not only these ideas are worth investing but they are so meant to be here in the current time. These are some of the best intriguing ideas which will give you a perfect start to your startup.