This was the 1st spec i had created that was open ended (OE) and I am intending on keeping it this way, since it gives a little more flexibility for the player. This is an Unholy Death Knight spec.
Click to see spec on WoWHead
The main point of this spec was and still is to keep your diseases on your enemies at all times, which Unholy Blight does a great job of. This will also allow the Death Knight more runes to use Festering Strike (to change frost and blood runes into death runes) while using your 2 Unholy runes into Scourge Strike (which is one of your primary damage ability). While your runes are recharging, Death Coil (which is also one of your other primary damage abilities) will be your attack of choice. Not only will this deal some decent damage, but it will also power up your Ghoul minion. For times in which you need more damage to be thrown around, Glyph of Unholy Frenzy will allow you to use Unholy Frenzy without worry of taking more damage. Also, ensure you are using Unholy Presence.
As for survivability, there are several abilities in this spec to help when the Death Knights own demise seems inevitable. Thankfully, once you have built up all of your death runes, this spec can use 4 consecutive Death Siphons. To follow that, you can target yourself and cast Lichborne (I recommend making a macro to do that for you)
/target (your characters name without the parenthesis)
Then proceed to cast Death Coil on yourself until you have enough health, or have run out of runic power (and these still increase your Ghoul’s power and add up to be able to cast Dark Transformation). Also, every time you cast your Death Coil, Runic Corruption has a 45% chance to proc, allowing your Runes to be ready sooner (possibly some as Death runes, if you have just used Festering Strikes). Remorseless Winter is also useful if you need to back away from a few enemies or be able to stop them dead in their tracks for a few seconds for a little breathing room. Glyph of Anti-Magic Shell will stop enemy caster from hitting you, and will also supply you with more needed runic power to cast more Death Coils. Also, if you want a faster way to develop your Dark Transformation, you can have your ghoul go to the fray first, using spare rune power to heal your pet for only 20 (instead of 40 due to Glyph of Death’s Embrace) which will get you 5 stacks of Shadow Infusion with only 100 runic power instead of 200.
As for the Open Ended (OE) part of this spec, I have left the choices of Death’s Advance, Chilblains, and Asphyxiate, as well as 1 major Glyph. I like Asphyxiate, but the times when they other 2 are usable, they really shine in their niches. As for the Major Glyph opening, there are several good choices. Outbreak may not be too great of a choice, due to this spec needing to use its Death Coil. However, Death Coil can help protect your friends, while Pestilence could be of use while your Unholy Blight is on cool down. Death Grip is good for giving a better range, but if you are soloing, then Unholy Command is a better choice.
Keep a high Mastery (to increase shadow damage) and Critical Strike chance (also for damage) to allow your strikes to keep as much power as possible. This way, your Scourge Strikes and Death Coils are always dealing as much damage as possible. Also, make sure you keep an eye on how long your diseases have left on them, since it’s better to use a Festering Strike than to need to re apply your diseases.