as always , I'd recommend you blockchain.info one. If you're not using large amounts of bitcoin and want to transfer it quickly, then I'm suggesting you that one. I've been using it since I've started getting into bitcoin and never had any problem whatsoever. But if you're trading with larger amounts, then I'd suggest you some desktop wallet over the online one but I'm not a fan of desktop wallets because of the syncing and whatnot, so it's kind of more easier to use the fast online one and it's secured  as much as you're secured and careful how you're handling it. Cheers!