Maul. Yeah, don't macro that; it's bad. Not as bad as remapping half your keybinds and learning to tank again, but worse than the week after when your fingers know where to go again. Which is exactly what I did a couple weeks ago.
Way back when I was posted all about this epiphany I had to avoid adding another key to press in bear form. I didn't have enough rage to always use maul, but I could narrow down on a percentage on how often I could use it and use castsequence macro lines to randomize my mauling accordingly. That actually worked quite well during combat, but the drawback was the RNG of mauling immediately when pulling with limited rage. It made grabbing snap aggro just a little harder. That got to be a little much over time and I decided to make a change.
At the same time I was actually leveling my new goblin warrior and had just gotten heroic strike. Of course I hadn't macroed it immediately after getting it seeing as I had a ton of space on my bars. So I was getting used to the idea of using a rage dump. So between those two influences I ended up combining growl and challenging roar into a single keybind and using a modifier key to access my sparingly used "AOE taunt". I actually used that a lot more in wrath. Anyway, that freed up the spot I needed to toss maul out on it's own.
The initial transition was painful... like really painful. I was pretty frustrated the first couple instances I tanked that way. Of course I had decided while I was moving buttons around that I should start using my 'Z' key as well and move the weapon sheathing/toggling button to '\' which I remember using for some FPS once upon a time. That let me move my interrupt from 'T' to 'Z' and whatever I had on '6' to 'T'. I'm using one of those natural keyboards so '6' is just just out of reach without a handgasm (the strange sensation of trying to spread the tips of your middle and index fingers as far apart as possible). On the bright side I am now using every possible key within reach of my left hand. Was tempted to use 'X' too, but I like to swim/fly down sometimes for fun.
So for those with a puzzled look I should explain what my keybinds look like. I use WASD for movement. 'A' and 'D' still turn left and right rather than strafe. I tried the strafing, but sometimes I want to take my hand off the mouse and still be somewhat mobile. Holding the right mouse button and 'turning' achieves the same effect as strafing anyway so no great loss.
'3' and '4' are my bread and butter abilities that get spammed a lot. They are easily reached while holding 'W' or 'S' to move forward or backward while steering with the mouse. Remaining mobile while attacking is pretty important for melee and also pretty handy for casters at times. '1' and 'Q' are next with the next most frequently use abilities followed by '2' which slightly impairs my ability to move forward so I stick something I use once in a while (I can still move forward by hitting both mouse buttons).
'5' I use for a taunt or another less frequently used ability. I've always had my taunt on '5' for my death knight since there were a lot more abilities in my tanking rotation than my bear. I always took that as a bit of a disadvantage seeing as taunt should in theory be more readily accessible. In practice I've found the opposite to be true; now that my taunt key is not immediately accessible I am hitting it much less in error so that when I do need it I'm more likely to have it off cooldown. After all I had it on '4' previously and '4' is one of the two buttons I hit the most for every other spec. Can't fight muscle memory.
Then my new addition 'Z' is where I stick my interrupts, they used to be over on 'T' and that wasn't nearly as convenient while moving. 'E' I use for AOE, 'R' for charging, death gripping, jumping back, blinking, basically anything that gets me to where I want to be or brings the where to me. 'T', 'F' and 'G' are reserved for cooldowns along with 'F1' and 'F2'. 'F3' I use for crowd control, 'F4' to break out of crowd control and 'F5' to reduce damage taken. Exceptions exist for classes without such abilities.
'C' I use for cleansing, 'V' for sprinting, dashing, moving faster by some means and 'B' I use for buffing. I actually have been macroing my 'B' to buff out of combat or with a modifier and than use some sort of cooldown I don't want to accidentally hit out of combat only while in combat. Mark of the Wild and Barkskin in the case of my druid. I used to use 'V' for mana regen, but decided to just leave that over with my mana potions and utility crap and click it as needed. A keybound speed boost has proven much more valuable in practice.
And finally that poor '6' key is still looking for a use. It is actually further of a reach for me than 'F5' so I've been experimenting with long cooldowns there, but really I've been clicking it more with the mouse than actually hitting '6'. Previously I used '6' for my start of a fight prep type key, hunter's mark, stealth, etc. So in reality I didn't add a key to my repertoire so much as add one, remove one and move two. Right now I'm still leaving '6' empty on my druid since it is so close to 'T' and I still slip once in a while trying to stealth. Once I grow out of that I'm sure I'll find a use for it. Moral of the story is get your binding right the first time and hopefully this long winded explanation helps someone.