I was recently looking for a sliding qwerty keyboard phone and to my dismay I realised that while we weren't looking, the NSA took them all away!
In my quest I found a phone database where you can search by features (I forget which one right now) and sorted through all possible candidates. My hopes went up momentarily when I saw the Dell Venue Pro[1] before I clicked "next" and saw how wrong they got it[2].
Eventually I sumbled on the Motorola Photon Q[3] - which I'm not even supposed to have, as it doesn't come with a SIM slot at all. Luckily some enterprising Korean guys have figured out the modding process and are selling them on ebay. I tried my luck and received it a few days ago. Really good value for money, loving the sliding action and physical keys but wish it were a bit more powerful. I think I've compensated for this mostly by cutting out a lot of fat and its puny dual core CPU now runs 4.4 fairly comfortably. I'll probably go back to my Nexus 5 soon but it's a great backup phone and I love the keyboard.
I'm half convinced that a custom N4/5 backplate with a built-in keyboard would sell like crazy. #kickstarterideas
TL;DR: Look at Moto Photon Q.
[1] http://upload.wikimedia.org/wikipedia/commons/7/7c/Dell_Venu...
[2] http://cdn.slashgear.com/wp-content/uploads/2010/10/dell_ven... I literally burst out laughing as soon as I saw this. Bless you, Dell. (also: windows)
[3] http://upload.wikimedia.org/wikipedia/commons/8/8d/Motorola_...