Listing down few of the crypto exchanges for various trading type:
Spot Trading BTC/Alts:
GDAX, Bitfinex - Proven track record
Altcoins Trading:
Binance - A new comer to the altcoin scene rapidly gaining popularity for shitcoins. Run & administered by the ex-Okcoin CTO. Very popular with a better UI & selection than bittrex . My personal choice and highly recommended!
Here's my referral link to join Binance: https://www.binance.com/?ref=12891300
Bitcoin Futures Trading:
Bitmex - Proven track record. A great platform with high leverage available
Bitcoin Options Trading:
Deribit - A newcomer to the scene but growing rapidly
Forex/Commodity/Stocks Trading:
1broker - Without a doubt, the cheapest & best CFD platform to use with your bitcoin. Including copy trade features. Proven track record
Feel free to suggest more and I will keep updating the list.