Where can one buy unlocked phones?

[outlooker]

Hello everyone,
I'm wondering where one should buy a factory unlocked smartphone, that never had anything to do with a carrier. I know you can buy some phones like the Nexus 5, BlackBerry Z10, etc straight from the Manufacture's official website and they deliver it to you with original warranty and everything intact. But what about other phones? I'm a T-Mobile customer and I plan on purchasing the LG G3 when it comes out, and I was hoping I could get one unlocked. I simply cannot stand my carrier putting its ugly logo and ruining the beauty of a phone. But on the other hand, if you buy from your carrier; you can just walk into your carrier's local store and get the phone exchanged in case it gives you any trouble. My previous phone (a Nexus 4) simply died for no reason but I got it replaced for free because I bought it from T-Mobile. However, if you buy an unlocked phone from Amazon or a similar website and it give you trouble you're pretty much screwed.
Is there a place where one can buy a factory unlocked phone that comes with a warranty and can be replaced if it turns out to be defective? I believe bestbuy.com sells some unlocked phones, if it sells an unlocked G3 when it comes out and it turns out to be defective, could I just walk into my local Best Buy and have it replaced?
What are my options?
Thanks in advance?

 

[Ry]

Best Buy sells unlocked phones. Looks like a lot of them too: New : unlocked phones - Best Buy

I know Fry's has unlocked phone in-store as well. Fry's Electronics |

If you didn't purchase from Best Buy, they have no reason to support you. Same for Fry's.

Motorola sells the Moto X and Moto G unlocked on their site. Warranty support will come from them.

Same goes for HTC with the One (M8) and One.

And Sony has a wide selection of unlocked phones.