My Samsung Galaxy S5.
On paper, it's the bee's knees. It looks great and it felt great to play with in the shop. But when I took it home, it wasn't comfortable to use like my iPhone 5S. You can't have apps and folders together in the apps draw, when playing games, my finger kept catching one of the touch sensitive keys, taking you out of the game, the little piece if plastic over the changing point is a nuisance and feels like it's going to break off at any time, the interface is laggy and inconsistent and awkward, the external speaker is very poor and tinny and if your phone's on a surface (which it is 90% of the time) the speaker grill is covered over making the sound muffled. RAM usage always seems to be at 90%, photos came out blurred far too often, which rarely happened on my iPhone, there's no permission control like the iPhone 5S, so apps such as Facebook were doing all kinds of things in the background, usually draining my battery.
I thought the Galaxy S5 was better than the iPhone 5S but in every benchmark test I did comparing them, the iPhone 5S won every time.
It's 6 months later and I still don't like it.