Well had an arguement with a friend over this last time we played.

He argued it was a shooting attack so it should get the benefit, I argued it was a special attack in the shooting phase and therefore it didn't.

Your thoughts?

From the BRB FAQ:

Q: Do Breath Weapon hits benefit from any other special rules,
equipment or magic items of the model that inflicts the hits? (p67)
A: No.

Although spells are not explicitly named in that question, "special rules" is arguably wide enough to apply to bonuses from Flaming Sword of Rhuin or other augments, such that the breath weapon attack would not benefit from it.

There is an entire section of the Rulebook called "Special Rules."

Most people I know play that if a spell conveys an ability listed in the "Special Rules" section of the Rulebook, that does not apply to Stomps and Breath Weapons (per the FAQ quoted by Haagrum).

But if a spell conveys an ability NOT listed in the "Special Rules" section of the Rulebook, that DOES apply to Stomps and Breath Weapons.

In the case of Flaming Sword, it conveys 3 effects: (1) +1 to wound; (2) magical attacks; and (3) "the Flaming Attacks special rule".

Only the third effect is a "Special Rule" and so it does not apply to Breath Weapons and Stomps -- but the other 2 do.

Well, if we need to talk about what is a special rule, then so be it.

Let's read BRB p.66, bottom left margin: That means that a minority of special rules are NOT in the special rule section p.66 to 79.What you describe is a house rule. It is certainly not a correct BRB interpretation, since the BRB mentions that some special rules are not in that section, as I recalled above.

If you want to know better what is a special rule, in the BRB sense, then better read p.66, bold paragraph below title:-=-=-

Back to original discussion,
In the case of Flaming Sword, it conveys 3 effects: (1) +1 to wound; (2) magical attacks; and (3) "the Flaming Attacks special rule".
All three effects are certainly uncommon rules to govern uncommon circumstances. They are all three special rules, according to BRB and despite some commonly played house rules.

Page 66 of the Rulebook says that the list of Special Rules in that section is not exhaustive. But the reason given is that "Many troop types have their own unique abilities laid out in their Warhammer Armies book." I think it's a stretch to say that anything not contained in the first 63 pages is a "Special Rule."

@ Dyvim tvar
I don't go as far as to say "anything". Choosing your army is not a special rule!

What I remind is:
- BRB's special rules are not limited to p.66-78.
- Any uncommon rule to govern uncommon circumstances is a special rule.
I provided quotes to justify these two arguments.

Reversely, I still cannot see any valid argument to deny the quality of "special rule" to the whole flaming sword's effects.
It is a rule, it is uncommon, and the circumstance are uncommon. What else would you require?

Simple.

It should be listed either in the "Special Rule" section of the Rulebook, or that it be listed as a "Special Rule" in the unit entry of an Army Book.

That's a common perception.
Unfortunately for this (mis)perception, the BRB itself, p.66 bottom left margin, indicates that the special rule section is NOT exhaustive, even when considering only BRB special rules.