You should look within for this answer, not ask someone else. What do you have an interest in? This is the question only you can answer.
Trading is about buying and selling something and hopefully making a profit. The reward is knowing that you made a profit by making the right call.
Now if you want to be a good trader...you have to have an affinity for your profession. Let's say you could trade toasters, or vacum cleaners with a broker. Might not be very rewarding for some but the principles are all the same...just like any market.
I love trading currencies and currency futures. Fasinates me for some unknown reason. Took me a while to find out though. I traded the indexes for a while. I have not even looked at an index in a couple years and I couldn't be happier.