Kraken – www.kraken.com

Liquidity:
Fast funding and low fees Bitcoin dark pool
Reliability:
24/7/365 support Legally compliant
Security:
Ranked #1 security Encrypted cold storage
Bitcoin Margin Trading:
Leveraged trading up to 5x Shorting allowed
Advanced Order Types:
Stop-loss orders Automate your strategy
Proof of Reserves Audits:
Cryptographically verified Pioneered the industry standard

https://www.kraken.com/