Rs. 20 per trade....irrespective of lot size. (Zerodha)
If trading more than 50 roundtrips per month - RKSV's Freedom Plan - Unlimited trading for Rs.1947 (~Rs. 2200 with taxes).
Or you can try Achiievers.
1499 for 3 months unlimited trading in F&O
I have an account with them for last few months. If you trade in options then you wont find one competitive to them.
For more reviews you can put a post in TraderRavi thread. A few members visiting there has opened an account with Achii.