Love it, like it, or hate it, the HTC One M9 is the current pinnacle of the HTC One series, and as such, commands a pretty heft price when purchased new. The refurbished/open box price, however, has been steadily dropping. Back in September it was available on eBay daily deals for $379, which we thought was a great price. Today, the price has fallen even lower to just under the three Benjamin mark to $299. That's a pretty awesome price for a current-gen flagship.
Of course, being an open box item, there is a chance the phone may have some slight blemishes. Let's be honest though, no device that you carry with you everywhere is going to stay flawless for long. Even though it is an open box item, it is still covered under an HTC warranty, which should give you confidence in your purchase.
The M9s being sold are unlocked, but they were originally AT&T devices. As such, they will work great on AT&T and should also work well on T-Mobile's LTE network and HSPA+ in areas that have been re-farmed to 1900MHz. There is the slight problem of the AT&T logo on the back, but if that embarrasses you, you could always cover it with a My Little Pony sticker, or just pretend it's a Death Star (that would make John Legere happy).
As of the time of publication, there are still grey and silver/rose-gold models available, but at this price that may change soon. The seller will ship the phone for free anywhere in the US, including Alaska and Hawaii, and sales tax will only be charged in the state of California. You can also pay extra to have it shipped to Europe, Canada, Japan, Australia, New Zealand, or Costa Rica. If you want it, now's the time to buy it.