These macros are primarily for a Frost Tank as they use abilities you can only get in the Frost tree such as Howling Blast and Frost Strike. You can modify them to fit whichever tree you're tanking from fairly easily just by being aware of what runes each skill uses.
There are two one button spam macros I use for the Death Knight that work really well. I've broken them into AoE Tanking and Single Target Tanking, but you can modify them slightly to support a little bit of each if needed, it depends how much AoE and Single Target threat you need per fight so you can have more than just the two macros below if you wanted as you hybrid some. Both Macros use a castrandom Rune Strike which as you know costs 20 runic power, you're challenge using these macros is going to be keeping your runic power down. Rune Strike does a pretty good job except on bigger fights where you probably want to dump it with a few Frost Strikes. What I usually do is shut off my macro or stop pressing it and press another hotkey that does Frost Strike. I usually wait till I have more than 80 Runic Power and fire off 2 in a row, but you can do what you prefer instead.
Death Knight Single Target Tanking
This macro is mainly for single target or boss fights, it will rotate each of your 6 runes on a consistent basis. It allows for you to start the right with Death and Decay if you wish because that uses 1 of each rune, it won't affect the sequence. There are substitutions you can make if you want this macro to be Single Target heavy with a little bit of emphasis on AoE, assuming the AoE macro doesn't work the way you want, I find that for all the situations I've been in it has, but here is what you can do.
You can replace one of the two Blood Strikes with Blood Boil, or you can replace them both with Pestilence and a Blood Boil, or maybe just one of them with Pestilence. It's really your choice but all those options will work for AoE substitutes.
/castsequence reset=shift/combat Plague Strike, Icy Touch, Blood Strike, Plague Strike, Icy Touch, Blood Strike
/castrandom Rune Strike
Death Knight AoE Tanking
Oftentimes, especially in 5 man groups I just leave this macro up even for boss fights because it does so well. You'll probably want to have Glyph of Howling Blast on your character to getup a Frost Fever for Pestilence to spread, but what I've found is that just the Plague Strike and Icy Touches combined with random Rune Strikes is enough to keep threat in 5 mans for sure and sometimes even raids. You'll still have to do a Runic Power dump and spam some Frost Strike in though.
/castsequence reset=shift/combat Howling Blast, Blood Boil, Plague Strike, Icy Touch, Pestilence
/castrandom Rune Strike
