Bitmex is an exchange with a unique feature. It allows you to trade Bitcoins with leverage. The leverage could be 100x, and it is a very interesting option not found in other exchanges.
Dash is a cryptocurrency, that has a built-in mixing service, to improve privacy. Since it's creation, it has an increased fee InstantX transaction. With InstantX a transaction is flagged "confirmed", immediately, for over the counter transactions. The transaction's input addresses are blocked till transaction is confirmed by the miners, to avoid double spending. See other posts about trading
Kraken is the top exchange for euro bitcoin traders. The trading platform, which is arguably the best of all the bitcoin exchanges, is number one in terms of BTC/EUR trading volume. Kraken holds the majority of bitcoin offline - cold storage, in other words - with "air gap" isolation from any online network, making hacking theft nearly impossible. See other posts about trading