My favorite one so far is Bittrex because they are wokring great so far for me and didnt had any problems with them.Next one is Binance because they are paying me gas $ for my neo that i hold there
Those are the real trusted exchanges right now but I still have my account on Poloniex where I put a huge part of my holdings, I still believe on this exchange and I really have to trust poloniex. I heard so many negative reviews about poloniex but I know Poloniex are still a secured exchange.