I have used:
Bitfinex (My favorite, good liquidity, many currencies, nice interface, many trading features). It has received some criticism on forums but I have never experienced any problems except for the hack 2016.
Bitstamp (my favorite for fiat deposits in EUR because they have SEPA deposits, good security, good liquidity, and simple interface). However, they have limited currencies and limited trading features.
Kraken (good security, many currencies, and good liquidity). Very old interface and slow site.
Bittrex (decent trading platform but not my favorite and some criticism on forums)
Poloniex (Was a good platform for alternative crypto markets 2 years ago. Now there are better platforms like Binance)
CEX (good support, a decent number of currencies, good security, limited liquidity)
You can read deep reviews about many different trading platforms at Cryptocointrade
HAPPY TRADING
