Is there a mod that automatically turn on my autoattack when I use a special, even if I don't have the rage for it? (I could have sworn the default UI did this once upon a time).

The default ui only can stop auto-attacking on target change.
you might want to create a macro containing "/startattack"

There used to be an excellent mod that automatically switched on auto-attack when you switched targets, were attacked, etc- but it was broken in 2.0

I've done as above poster says, and simply made

/startattack
/cast 'some skill'

macros for my warrior and rogue.

Pressing 't' turns on autoattack by default for what it's worth.

Clarification: Pressing 't' TOGGLES autoattack.

Can't you just right click the target to auto attack and then right click again to stop?

I've had almost all of my abilities set up this way for quite a while. I highly recommend adding "#show none" at the top of each macro. My framerate improved drastically when I changed them all from "#showtooltip <whatever>" to "#show none".

Of course, this means you dont want to put the macros directly on bars -- #show none means you wont get any cooldowns, range coloring, or anything else like that. I bind keys to the macros with spellbinder, and for abilities where I need to see cooldowns or range, I just drag the ability straight from the spellbook onto a button with no keybindings.

Also, "/startattack [harm,exists,nodead]" instead of just "/startattack" reduces error spam. The ability cast will provide all the error spam you could possibly want, no need to double it up.

On every character I have:

Shows your weapon icon, pressing it will turn on autoattack. Pretty simple.

edit: I guess its on my "General Macros" list, I should say, but same difference.

I'm not 100% certain, but couldn't you achieve the exact same by simply dragging the 'Attack' button from the General page of your spellbook onto your action bar? The only reason I can think of for not doing that if you want an auto-attack button is if the blinking it does when auto-attacking annoys you.

I use a "3 in 1" button macro.

/cast [harm] Sinister Strike
/startattack
/dismount
/use [noharm] Reins of the Cobalt War Talbuk

If targeting nothing, or targeting a friendly, you will mount up. If you are on a mount, you will be dismounted. However, if targeting an enemy, you will start auto attacking as well as Sinister Striking (spamming the key won't toggle auto attack, no damage loss). This can be replaced with Backstab, Bloodthirst or whatever you primarily attack with.

I have my flying mount on the next key over, which is also my primary finisher (SnD) and can be anything as well.

/cast [harm] Slice and Dice
/dismount
/use [noharm] Swift Green Gryphon

A bit simpler since there is no auto attack start.

Change the ability/mount and you've got what you were asking for plus a mount key.

The one problem with that is, if for some reason, you hit the button/hotkey when auto-attack is already on, you would end up turning it off. Also, if you have it on a hidden action bar, the blinking isn't an issue. I guess having it set to #show none would achieve the same effect if you had it on a visible action bar as well.

Same does /StartAttack, except the toggle part.
I've converted all my attacks into a macro starting with /StartAttack, just like Cesar2000 did.

And for purely historical enjoyment, you could check out my old thread, where I was asking the very same question before the /StartAttack command was available.

Just make sure you replace them for PvP if you're a button masher.

I thought /startattack was spammable?

I have Backstab and Sinister Strike macros that feature /startattack, and they are indeed spammable in the sense that it won't turn off your auto attack. I find it's a great way to start attacking a new mob, even if I don't have energy for a Backstab. Is that what you meant?

Yeah. The old macros always were subject to turning off your autoattack if you spammed them(or at the minimum reseting it), which is why I asked.

You'll get used to it quite quickly though.
That is, if you have a decent bar for your energy.

It's fairly easy to get used to, it just reduces the margin for error in certain situations.

I had the problem of pressing my startattack macro...

/startattack
/cast Backstab

...right when 1 mob would die, which caused me to lose a target, then hit the nearest target, possibly breaking some form of CC.

Because i always tab i want to dps, but still be able to start autoattack it if i don't have the energy/positioning for Backstab, i came up with this macro

/stopmacro [noexists]
/startattack
/cast Backstab

This will start auto attacking as long as you have a target, so no more accidentally breaking CC.

About accidentally braking cc: Is there any way to prevent automatic targeting of a mob that you have not actually selected? This happens when you have no target and a mob attacks you or when you use a special attack while standing near a mob. It causes me to brake sheeps all the time when my current target dies and I cannot even do anything about it other than walking away or stop using specials when a mob has low life.

That /stopmacro [noexists] helps in some cases, but it is not really reliable in the event of unlucky timing.