Nathyrra's 0/20/51 "ShadowFrost" Spec:
http://www.wowhead.com/?talent=jZGMxzbxZfMGI0okxcqMcsuh
This is the spec I've theorycrafted for a while ever since the 3.0.8 PTR started with the announced changes (more specifically, nerfs). Without going into it too much, this spec strengthens the weakest parts of a typical DK rotation (icy touch, blood strike), and instead turns them into extremely potent burst, utility, and control.
The premise behind this spec is to offer amazing burst that not only penetrates armor, but is also reliable at the same time with the new Killing Machine mechanics. It essentially turns your Icy Touch into a burst that can be consistently higher damage than Scourge Strike that not only has a 30 yard range, but also only costs 1F rune instead of 1F1U. It allows quick swaps with amazing burst potential, as you can see here from prelimary PTR testing:
With Rune of the Fallen Crusader:
Icy Touch -
http://img502.imageshack.us/img502/3481/it2oe1.jpg
Scourge Strike -
http://img253.imageshack.us/img253/7188/ss2tn1.jpg
With Rune of Cinderglacier:
Icy Touch -
http://img522.imageshack.us/img522/4779/it1lk0.jpg
Scourge Strike -
http://img253.imageshack.us/img253/5893/ss1ne2.jpg
I won't get into more of the finer details regarding this spec, but there's a specific reason for every point placement and I feel after testing the spec in a long night of 3v3 that it definitely has the potential that I thought it would. The synergy between the opposite ends of the talent trees used is very strong as I expected. I consider this spec extremely potent in its ability to target anyone regardless of the armor they wear, as well as being excellent for putting out enormous spread damage.
The biggest weaknesses of this spec are not having access to Bladed Armor (resulting in about 400-500 less AP) and also not having (Improved) Rune Tap which can make or break certain match ups.